+1.  Have been having constant, ongoing issues with wifi dropouts - but only with 12.04 and only in the last several weeks (did not seem to be a problem when I was running beta1.  Came up later than that).

I have this on two machines, running Xubuntu and Ubuntu respectively, but both 12.04 and both current/up-to-date.

https://bugzilla.redhat.com/show_bug.cgi?id=805285 suggests it might be an Intel thing. (see also http://bugzilla.intellinuxwireless.org/show_bug.cgi?id=2359) - if it's the same thing.

Very hard to work out what's relevant and what's not from my Syslog (found the redhat link from a search for "iwlwifi 0000:03:00.0: fail to flush all tx fifo queues" as one line appearing in my syslog frequently enough)

The symptom is that I appear to remain associated, but all IP traffic stops, and a continuous ping shows my local wifi interface IP reporting 'destination host unreachable' (pinging my default gateway) after a period.  It can take quite a while (if at all) for the wifi association to drop and restart, getting me comms back. Doing so manually also gets me comms back - for a while.  
Over the last 2.5 hours, searching for 'reason=' in my syslog:

May  8 18:25:04 hawkeye kernel: [  260.422424] wlan0: deauthenticating from 00:14:6c:b0:9e:02 by local choice (reason=3)
May  8 18:25:08 hawkeye wpa_supplicant[2079]: CTRL-EVENT-DISCONNECTED bssid=00:00:00:00:00:00 reason=3
May  8 18:25:08 hawkeye kernel: [  263.732721] wlan0: deauthenticating from 00:14:6c:b0:9e:02 by local choice (reason=3)
May  8 18:25:11 hawkeye wpa_supplicant[2079]: CTRL-EVENT-DISCONNECTED bssid=00:00:00:00:00:00 reason=3
May  8 18:25:11 hawkeye kernel: [  267.051132] wlan0: deauthenticating from 00:14:6c:b0:9e:02 by local choice (reason=3)
May  8 18:25:14 hawkeye wpa_supplicant[2079]: CTRL-EVENT-DISCONNECTED bssid=00:00:00:00:00:00 reason=3
May  8 18:25:14 hawkeye kernel: [  270.401257] wlan0: deauthenticating from 00:14:6c:b0:9e:02 by local choice (reason=3)
May  8 18:25:18 hawkeye wpa_supplicant[2079]: CTRL-EVENT-DISCONNECTED bssid=00:00:00:00:00:00 reason=3
May  8 18:25:18 hawkeye kernel: [  273.815477] wlan0: deauthenticating from 00:14:6c:b0:9e:02 by local choice (reason=3)
May  8 18:25:21 hawkeye wpa_supplicant[2079]: CTRL-EVENT-DISCONNECTED bssid=00:00:00:00:00:00 reason=3
May  8 18:25:21 hawkeye kernel: [  277.149726] wlan0: deauthenticating from 00:14:6c:b0:9e:02 by local choice (reason=3)
May  8 18:25:25 hawkeye wpa_supplicant[2079]: CTRL-EVENT-DISCONNECTED bssid=00:00:00:00:00:00 reason=3
May  8 18:25:25 hawkeye kernel: [  280.527970] wlan0: deauthenticating from 00:14:6c:b0:9e:02 by local choice (reason=3)
May  8 18:25:28 hawkeye wpa_supplicant[2079]: CTRL-EVENT-DISCONNECTED bssid=00:00:00:00:00:00 reason=3
May  8 18:25:28 hawkeye kernel: [  283.814223] wlan0: deauthenticating from 00:14:6c:b0:9e:02 by local choice (reason=3)
May  8 18:25:31 hawkeye wpa_supplicant[2079]: CTRL-EVENT-DISCONNECTED bssid=00:00:00:00:00:00 reason=3
May  8 18:25:31 hawkeye kernel: [  287.160435] wlan0: deauthenticating from 00:14:6c:b0:9e:02 by local choice (reason=3)
May  8 18:25:34 hawkeye wpa_supplicant[2079]: CTRL-EVENT-DISCONNECTED bssid=00:00:00:00:00:00 reason=3
May  8 18:25:34 hawkeye kernel: [  290.426766] wlan0: deauthenticating from 00:14:6c:b0:9e:02 by local choice (reason=3)
May  8 18:25:38 hawkeye wpa_supplicant[2079]: CTRL-EVENT-DISCONNECTED bssid=00:00:00:00:00:00 reason=3
May  8 18:25:38 hawkeye kernel: [  293.705106] wlan0: deauthenticating from 00:14:6c:b0:9e:02 by local choice (reason=3)
May  8 18:25:41 hawkeye wpa_supplicant[2079]: CTRL-EVENT-DISCONNECTED bssid=00:00:00:00:00:00 reason=3
May  8 18:25:41 hawkeye kernel: [  297.051485] wlan0: deauthenticating from 00:14:6c:b0:9e:02 by local choice (reason=3)
May  8 18:54:12 hawkeye wpa_supplicant[2079]: CTRL-EVENT-DISCONNECTED bssid=00:14:6c:b0:9e:02 reason=1
May  8 20:16:52 hawkeye kernel: [ 6956.345223] wlan0: deauthenticating from 00:14:6c:b0:9e:02 by local choice (reason=3)
May  8 20:16:52 hawkeye wpa_supplicant[2079]: CTRL-EVENT-DISCONNECTED bssid=00:00:00:00:00:00 reason=3
May  8 20:18:06 hawkeye wpa_supplicant[2079]: CTRL-EVENT-DISCONNECTED bssid=00:14:6c:b0:9e:02 reason=1
May  8 20:19:11 hawkeye wpa_supplicant[2079]: CTRL-EVENT-DISCONNECTED bssid=00:14:6c:b0:9e:02 reason=1
May  8 20:20:15 hawkeye wpa_supplicant[2079]: CTRL-EVENT-DISCONNECTED bssid=00:14:6c:b0:9e:02 reason=4
May  8 20:25:18 hawkeye wpa_supplicant[2079]: CTRL-EVENT-DISCONNECTED bssid=00:14:6c:b0:9e:02 reason=4
May  8 20:26:08 hawkeye wpa_supplicant[2079]: CTRL-EVENT-DISCONNECTED bssid=00:14:6c:b0:9e:02 reason=4
May  8 20:26:40 hawkeye wpa_supplicant[2079]: CTRL-EVENT-DISCONNECTED bssid=00:14:6c:b0:9e:02 reason=4
May  8 20:27:51 hawkeye wpa_supplicant[2079]: CTRL-EVENT-DISCONNECTED bssid=00:14:6c:b0:9e:02 reason=1
May  8 20:28:16 hawkeye wpa_supplicant[2079]: CTRL-EVENT-DISCONNECTED bssid=00:14:6c:b0:9e:02 reason=4
May  8 20:46:42 hawkeye wpa_supplicant[2079]: CTRL-EVENT-DISCONNECTED bssid=00:14:6c:b0:9e:02 reason=4
May  8 20:47:50 hawkeye wpa_supplicant[2079]: CTRL-EVENT-DISCONNECTED bssid=00:14:6c:b0:9e:02 reason=3
May  8 20:47:50 hawkeye kernel: [ 8810.549212] wlan0: deauthenticating from 00:14:6c:b0:9e:02 by local choice (reason=3)
May  8 20:53:47 hawkeye wpa_supplicant[2079]: CTRL-EVENT-DISCONNECTED bssid=00:14:6c:b0:9e:02 reason=4
May  8 20:58:48 hawkeye wpa_supplicant[2079]: CTRL-EVENT-DISCONNECTED bssid=00:14:6c:b0:9e:02 reason=1



root@hawkeye:~# uname -a
Linux hawkeye 3.2.0-17-generic #27-Ubuntu SMP Fri Feb 24 15:37:36 UTC 2012 x86_64 x86_64 x86_64 GNU/Linux
root@hawkeye:~# lspci | grep Network
00:19.0 Ethernet controller: Intel Corporation 82577LM Gigabit Network Connection (rev 06)
03:00.0 Network controller: Intel Corporation Centrino Advanced-N 6200 (rev 35)
root@hawkeye:~# 

Ahh it just happened, and i'd not seen this before:

May  8 21:01:31 hawkeye kernel: [ 9629.845300] iwlwifi 0000:03:00.0: Queue 2 stuck for 2000 ms.
May  8 21:01:31 hawkeye kernel: [ 9629.845307] iwlwifi 0000:03:00.0: Current read_ptr 157 write_ptr 164
May  8 21:01:31 hawkeye kernel: [ 9629.845311] iwlwifi 0000:03:00.0: On demand firmware reload
May  8 21:01:31 hawkeye kernel: [ 9629.845711] ieee80211 phy0: Hardware restart was requested
May  8 21:01:31 hawkeye kernel: [ 9629.845783] iwlwifi 0000:03:00.0: L1 Enabled; Disabling L0S
May  8 21:01:31 hawkeye kernel: [ 9629.845969] iwlwifi 0000:03:00.0: Radio type=0x1-0x3-0x1
May  8 21:01:31 hawkeye kernel: [ 9630.412294] iwlwifi 0000:03:00.0: Queue 2 stuck for 2000 ms.
May  8 21:01:31 hawkeye kernel: [ 9630.412301] iwlwifi 0000:03:00.0: Current read_ptr 0 write_ptr 1
May  8 21:01:32 hawkeye kernel: [ 9630.911461] iwlwifi 0000:03:00.0: Queue 2 stuck for 2000 ms.
May  8 21:01:32 hawkeye kernel: [ 9630.911468] iwlwifi 0000:03:00.0: Current read_ptr 0 write_ptr 2
May  8 21:01:32 hawkeye kernel: [ 9631.410570] iwlwifi 0000:03:00.0: Queue 2 stuck for 2000 ms.
May  8 21:01:32 hawkeye kernel: [ 9631.410577] iwlwifi 0000:03:00.0: Current read_ptr 0 write_ptr 2
May  8 21:01:33 hawkeye kernel: [ 9631.909772] iwlwifi 0000:03:00.0: Queue 0 stuck for 2000 ms.
May  8 21:01:33 hawkeye kernel: [ 9631.909780] iwlwifi 0000:03:00.0: Current read_ptr 0 write_ptr 1
May  8 21:01:33 hawkeye kernel: [ 9631.909784] iwlwifi 0000:03:00.0: Queue 2 stuck for 2000 ms.
May  8 21:01:33 hawkeye kernel: [ 9631.909788] iwlwifi 0000:03:00.0: Current read_ptr 0 write_ptr 3
May  8 21:01:33 hawkeye kernel: [ 9632.408853] iwlwifi 0000:03:00.0: Queue 0 stuck for 2000 ms.
May  8 21:01:33 hawkeye kernel: [ 9632.408860] iwlwifi 0000:03:00.0: Current read_ptr 0 write_ptr 2
May  8 21:01:33 hawkeye kernel: [ 9632.408865] iwlwifi 0000:03:00.0: Queue 2 stuck for 2000 ms.
May  8 21:01:33 hawkeye kernel: [ 9632.408869] iwlwifi 0000:03:00.0: Current read_ptr 0 write_ptr 3
May  8 21:01:35 hawkeye wpa_supplicant[2079]: CTRL-EVENT-DISCONNECTED bssid=00:14:6c:b0:9e:02 reason=4
May  8 21:01:35 hawkeye kernel: [ 9634.613211] cfg80211: All devices are disconnected, going to restore regulatory settings
May  8 21:01:35 hawkeye kernel: [ 9634.613221] cfg80211: Restoring regulatory settings
May  8 21:01:35 hawkeye kernel: [ 9634.613228] cfg80211: Calling CRDA to update world regulatory domain
May  8 21:01:35 hawkeye NetworkManager[960]: <info> (wlan0): supplicant interface state: completed -> scanning
May  8 21:01:35 hawkeye kernel: [ 9634.619092] cfg80211: Ignoring regulatory request Set by core since the driver uses its own custo
m regulatory domain
May  8 21:01:35 hawkeye kernel: [ 9634.619098] cfg80211: World regulatory domain updated:
May  8 21:01:35 hawkeye kernel: [ 9634.619101] cfg80211:     (start_freq - end_freq @ bandwidth), (max_antenna_gain, max_eirp)
May  8 21:01:35 hawkeye kernel: [ 9634.619106] cfg80211:     (2402000 KHz - 2472000 KHz @ 40000 KHz), (300 mBi, 2000 mBm)

May  8 21:01:35 hawkeye kernel: [ 9634.619111] cfg80211:     (2457000 KHz - 2482000 KHz @ 20000 KHz), (300 mBi, 2000 mBm)
May  8 21:01:35 hawkeye kernel: [ 9634.619115] cfg80211:     (2474000 KHz - 2494000 KHz @ 20000 KHz), (300 mBi, 2000 mBm)
May  8 21:01:35 hawkeye kernel: [ 9634.619119] cfg80211:     (5170000 KHz - 5250000 KHz @ 40000 KHz), (300 mBi, 2000 mBm)
May  8 21:01:35 hawkeye kernel: [ 9634.619123] cfg80211:     (5735000 KHz - 5835000 KHz @ 40000 KHz), (300 mBi, 2000 mBm)
May  8 21:01:39 hawkeye wpa_supplicant[2079]: Trying to authenticate with 00:14:6c:b0:9e:02 (SSID='blakjak.net' freq=2437 MHz)
May  8 21:01:39 hawkeye wpa_supplicant[2079]: Trying to associate with 00:14:6c:b0:9e:02 (SSID='blakjak.net' freq=2437 MHz)
May  8 21:01:39 hawkeye kernel: [ 9638.025111] wlan0: authenticate with 00:14:6c:b0:9e:02 (try 1)
May  8 21:01:39 hawkeye kernel: [ 9638.026717] wlan0: authenticated
May  8 21:01:39 hawkeye kernel: [ 9638.027155] wlan0: associate with 00:14:6c:b0:9e:02 (try 1)
May  8 21:01:39 hawkeye NetworkManager[960]: <info> (wlan0): supplicant interface state: scanning -> associating
May  8 21:01:39 hawkeye kernel: [ 9638.058447] wlan0: RX ReassocResp from 00:14:6c:b0:9e:02 (capab=0x431 status=0 aid=2)
May  8 21:01:39 hawkeye kernel: [ 9638.058452] wlan0: associated
May  8 21:01:39 hawkeye wpa_supplicant[2079]: Associated with 00:14:6c:b0:9e:02
May  8 21:01:39 hawkeye NetworkManager[960]: <info> (wlan0): supplicant interface state: associating -> 4-way handshake
May  8 21:01:39 hawkeye NetworkManager[960]: <info> (wlan0): supplicant interface state: 4-way handshake -> group handshake
May  8 21:01:39 hawkeye wpa_supplicant[2079]: WPA: Key negotiation completed with 00:14:6c:b0:9e:02 [PTK=TKIP GTK=TKIP]
May  8 21:01:39 hawkeye wpa_supplicant[2079]: CTRL-EVENT-CONNECTED - Connection to 00:14:6c:b0:9e:02 completed (reauth) [id=0 id_str=]
May  8 21:01:39 hawkeye NetworkManager[960]: <info> (wlan0): supplicant interface state: group handshake -> completed
May  8 21:01:42 hawkeye kernel: [ 9641.393362] iwlwifi 0000:03:00.0: Queue 2 stuck for 2000 ms.
May  8 21:01:42 hawkeye kernel: [ 9641.393370] iwlwifi 0000:03:00.0: Current read_ptr 18 write_ptr 23
May  8 21:01:42 hawkeye kernel: [ 9641.393375] iwlwifi 0000:03:00.0: On demand firmware reload
May  8 21:01:42 hawkeye kernel: [ 9641.393837] ieee80211 phy0: Hardware restart was requested
May  8 21:01:42 hawkeye kernel: [ 9641.393913] iwlwifi 0000:03:00.0: L1 Enabled; Disabling L0S
May  8 21:01:42 hawkeye kernel: [ 9641.394103] iwlwifi 0000:03:00.0: Radio type=0x1-0x3-0x1
May  8 21:01:43 hawkeye kernel: [ 9641.960371] iwlwifi 0000:03:00.0: Queue 2 stuck for 2000 ms.
May  8 21:01:43 hawkeye kernel: [ 9641.960381] iwlwifi 0000:03:00.0: Current read_ptr 0 write_ptr 2
May  8 21:01:43 hawkeye kernel: [ 9642.224708] iwlwifi 0000:03:00.0: Not sending command - CT KILL
May  8 21:01:43 hawkeye kernel: [ 9642.224717] iwlwifi 0000:03:00.0: Error sending SENSITIVITY_CMD: enqueue_hcmd failed: -5
May  8 21:01:43 hawkeye kernel: [ 9642.459523] iwlwifi 0000:03:00.0: Queue 2 stuck for 2000 ms.
May  8 21:01:43 hawkeye kernel: [ 9642.459530] iwlwifi 0000:03:00.0: Current read_ptr 0 write_ptr 2
May  8 21:01:44 hawkeye kernel: [ 9642.958695] iwlwifi 0000:03:00.0: Queue 2 stuck for 2000 ms.
May  8 21:01:44 hawkeye kernel: [ 9642.958703] iwlwifi 0000:03:00.0: Current read_ptr 0 write_ptr 2
May  8 21:01:44 hawkeye wpa_supplicant[2079]: WPA: Group rekeying completed with 00:14:6c:b0:9e:02 [GTK=TKIP]
May  8 21:01:44 hawkeye kernel: [ 9643.052998] iwlwifi 0000:03:00.0: Not sending command - CT KILL
May  8 21:01:44 hawkeye kernel: [ 9643.053005] iwlwifi 0000:03:00.0: Error sending REPLY_ADD_STA: enqueue_hcmd failed: -5
May  8 21:01:44 hawkeye kernel: [ 9643.457830] iwlwifi 0000:03:00.0: Queue 2 stuck for 2000 ms.
May  8 21:01:44 hawkeye kernel: [ 9643.457837] iwlwifi 0000:03:00.0: Current read_ptr 0 write_ptr 2
May  8 21:01:45 hawkeye kernel: [ 9643.956975] iwlwifi 0000:03:00.0: Queue 2 stuck for 2000 ms.
May  8 21:01:45 hawkeye kernel: [ 9643.956982] iwlwifi 0000:03:00.0: Current read_ptr 0 write_ptr 2
May  8 21:01:45 hawkeye kernel: [ 9643.968114] iwlwifi 0000:03:00.0: Not sending command - CT KILL
May  8 21:01:45 hawkeye kernel: [ 9643.968120] iwlwifi 0000:03:00.0: Error sending SENSITIVITY_CMD: enqueue_hcmd failed: -5
May  8 21:01:45 hawkeye kernel: [ 9644.612760] iwlwifi 0000:03:00.0: Not sending command - CT KILL
May  8 21:01:45 hawkeye kernel: [ 9644.612768] iwlwifi 0000:03:00.0: Error sending SENSITIVITY_CMD: enqueue_hcmd failed: -5
May  8 21:01:46 hawkeye kernel: [ 9645.338574] iwlwifi 0000:03:00.0: Not sending command - CT KILL
May  8 21:01:46 hawkeye kernel: [ 9645.338585] iwlwifi 0000:03:00.0: Error sending REPLY_LEDS_CMD: enqueue_hcmd failed: -5
May  8 21:01:46 hawkeye kernel: [ 9645.338619] iwlwifi 0000:03:00.0: Not sending command - CT KILL
May  8 21:01:46 hawkeye kernel: [ 9645.338625] iwlwifi 0000:03:00.0: Error sending REPLY_LEDS_CMD: enqueue_hcmd failed: -5
May  8 21:01:46 hawkeye kernel: [ 9645.631852] iwlwifi 0000:03:00.0: Not sending command - CT KILL
May  8 21:01:46 hawkeye kernel: [ 9645.631860] iwlwifi 0000:03:00.0: Error sending SENSITIVITY_CMD: enqueue_hcmd failed: -5
May  8 21:01:47 hawkeye kernel: [ 9645.837742] iwlwifi 0000:03:00.0: Not sending command - CT KILL
May  8 21:01:47 hawkeye kernel: [ 9645.837751] iwlwifi 0000:03:00.0: Error sending REPLY_QOS_PARAM: enqueue_hcmd failed: -5
May  8 21:01:47 hawkeye kernel: [ 9645.837756] iwlwifi 0000:03:00.0: Failed to update QoS
May  8 21:01:47 hawkeye kernel: [ 9645.837762] iwlwifi 0000:03:00.0: Not sending command - CT KILL
May  8 21:01:47 hawkeye kernel: [ 9645.837767] iwlwifi 0000:03:00.0: Error sending REPLY_RXON: enqueue_hcmd failed: -5
May  8 21:01:47 hawkeye kernel: [ 9645.837771] iwlwifi 0000:03:00.0: Error clearing ASSOC_MSK on BSS (-5)
May  8 21:01:47 hawkeye kernel: [ 9645.837778] iwlwifi 0000:03:00.0: Not sending command - CT KILL
May  8 21:01:47 hawkeye kernel: [ 9645.837782] iwlwifi 0000:03:00.0: Error sending REPLY_RXON: enqueue_hcmd failed: -5
May  8 21:01:47 hawkeye kernel: [ 9645.837786] iwlwifi 0000:03:00.0: Error clearing ASSOC_MSK on BSS (-5)
May  8 21:01:47 hawkeye wpa_supplicant[2079]: CTRL-EVENT-DISCONNECTED bssid=00:14:6c:b0:9e:02 reason=4
May  8 21:01:47 hawkeye kernel: [ 9645.885680] iwlwifi 0000:03:00.0: Not sending command - CT KILL
May  8 21:01:47 hawkeye kernel: [ 9645.885688] iwlwifi 0000:03:00.0: Error sending REPLY_ADD_STA: enqueue_hcmd failed: -5
May  8 21:01:47 hawkeye kernel: [ 9645.885696] ieee80211 phy0: failed to remove key (0, 00:14:6c:b0:9e:02) from hardware (-5)
May  8 21:01:47 hawkeye kernel: [ 9645.885743] iwlwifi 0000:03:00.0: Not sending command - CT KILL
May  8 21:01:47 hawkeye kernel: [ 9645.885747] iwlwifi 0000:03:00.0: Error sending REPLY_REMOVE_STA: enqueue_hcmd failed: -5
May  8 21:01:47 hawkeye kernel: [ 9645.885752] iwlwifi 0000:03:00.0: Error removing station 00:14:6c:b0:9e:02
May  8 21:01:47 hawkeye kernel: [ 9645.885906] iwlwifi 0000:03:00.0: Not sending command - CT KILL
May  8 21:01:47 hawkeye kernel: [ 9645.885913] iwlwifi 0000:03:00.0: Error sending REPLY_RXON: enqueue_hcmd failed: -5
May  8 21:01:47 hawkeye kernel: [ 9645.885918] iwlwifi 0000:03:00.0: Error clearing ASSOC_MSK on BSS (-5)
May  8 21:01:47 hawkeye kernel: [ 9645.885949] iwlwifi 0000:03:00.0: Not sending command - CT KILL
May  8 21:01:47 hawkeye kernel: [ 9645.885953] iwlwifi 0000:03:00.0: Error sending REPLY_LEDS_CMD: enqueue_hcmd failed: -5
May  8 21:01:47 hawkeye kernel: [ 9645.885961] iwlwifi 0000:03:00.0: Not sending command - CT KILL
May  8 21:01:47 hawkeye kernel: [ 9645.885964] iwlwifi 0000:03:00.0: Error sending POWER_TABLE_CMD: enqueue_hcmd failed: -5
May  8 21:01:47 hawkeye kernel: [ 9645.885968] iwlwifi 0000:03:00.0: set power fail, ret = -5
May  8 21:01:47 hawkeye kernel: [ 9645.885972] iwlwifi 0000:03:00.0: Not sending command - CT KILL
May  8 21:01:47 hawkeye kernel: [ 9645.885976] iwlwifi 0000:03:00.0: Error sending REPLY_RXON: enqueue_hcmd failed: -5
May  8 21:01:47 hawkeye kernel: [ 9645.885980] iwlwifi 0000:03:00.0: Error clearing ASSOC_MSK on BSS (-5)
May  8 21:01:47 hawkeye kernel: [ 9645.957555] iwlwifi 0000:03:00.0: Not sending command - CT KILL


(etc)

I had to run 'modprobe -r iwlwifi; modprobe iwlwifi' to get this to come back (usually networkmanager would let me reassociate without drama, first time this has happened... but i also manually did the same earlier for the first time to see if it'd reset my connection, something i inferred from the redhat bug).

No idea whether this is related or different but I've heard that there's some known wifi issues in Linux 3.0.x...