I'll mirror the above reports, I'm using a Intel Corporation Centrino Advanced-N 6205 on Linux Mint 17 (Ubuntu 14.04 Trusty), I recently upgraded from 12.04 Linux Mint 16 (Ubuntu 13.04 Saucy) using a complete clean reinstall and now the problem manifests.

On Mint 16 (13.04) I had *no* wifi problems in my office (I've been here for 6 months). Since reinstalling 11 days ago with Mint 17 (14.04) in the office (with a BTHub) I'm kicked off of wifi every 5-15 minutes, at home (on a Virgin Wifi device) I have no connection problems. I believe the problem is a combination of 14.04 and the BTHubs here in the office (we have two, different SSIDs, I could use them both before, now both exhibit the same kick-me-off behaviour).

Currently I solve the problem using "sudo pkill wpa_supplicant" as discovered in this thread. This takes me back online, it feels very much like the same behaviour shown in this thread with 14.04 and for #1294044. Before discovering this bug report I was using the widget in the notification bar to disable and then enable the wireless device.

Re. "it tooks me ages to find this page" as others have noted - I've been hunting around with log messages for 11 days before I found this bug report, nothing else I found got me even close to a useful diagnosis.

$ uname -a
Linux ian-Latitude-E6420 3.13.0-24-generic #47-Ubuntu SMP Fri May 2 23:30:00 UTC 2014 x86_64 x86_64 x86_64 GNU/Linux

$ lspci
...
03:00.0 Network controller: Intel Corporation Centrino Advanced-N 6205 [Taylor Peak] (rev 34)

I have the latest firmware for the 6205 (verifying against Intel's site: http://www.intel.com/support/wireless/wlan/sb/CS-034398.htm)
$ sudo lshw -C network
  *-network               
       description: Ethernet interface
       product: 82579LM Gigabit Network Connection
       vendor: Intel Corporation
       physical id: 19
       bus info: pci@0000:00:19.0
       logical name: eth0
       version: 04
       serial: 5c:26:0a:61:e2:24
       capacity: 1Gbit/s
       width: 32 bits
       clock: 33MHz
       capabilities: pm msi bus_master cap_list ethernet physical tp 10bt 10bt-fd 100bt 100bt-fd 1000bt-fd autonegotiation
       configuration: autonegotiation=on broadcast=yes driver=e1000e driverversion=2.3.2-k firmware=0.13-3 latency=0 link=no multicast=yes port=twisted pair
       resources: irq:43 memory:e6700000-e671ffff memory:e6780000-e6780fff ioport:5040(size=32)
  *-network
       description: Wireless interface
       product: Centrino Advanced-N 6205 [Taylor Peak]
       vendor: Intel Corporation
       physical id: 0
       bus info: pci@0000:03:00.0
       logical name: wlan0
       version: 34
       serial: a0:88:b4:65:ed:7c
       width: 64 bits
       clock: 33MHz
       capabilities: pm msi pciexpress bus_master cap_list ethernet physical wireless
       configuration: broadcast=yes driver=iwlwifi driverversion=3.13.0-24-generic firmware=18.168.6.1 ip=192.168.1.65 latency=0 link=yes multicast=yes wireless=IEEE 802.11abgn
       resources: irq:45 memory:e6600000-e6601fff

A typical dmesg (from when the problem first starts to the wifi being offline):
[22291.312726] wlan0: deauthenticated from 00:81:d8:64:33:4a (Reason: 6)
[22291.344445] cfg80211: Calling CRDA to update world regulatory domain
[22291.351954] cfg80211: World regulatory domain updated:
[22291.351963] cfg80211:   (start_freq - end_freq @ bandwidth), (max_antenna_gain, max_eirp)
[22291.351998] cfg80211:   (2402000 KHz - 2472000 KHz @ 40000 KHz), (300 mBi, 2000 mBm)
[22291.352004] cfg80211:   (2457000 KHz - 2482000 KHz @ 40000 KHz), (300 mBi, 2000 mBm)
[22291.352009] cfg80211:   (2474000 KHz - 2494000 KHz @ 20000 KHz), (300 mBi, 2000 mBm)
[22291.352013] cfg80211:   (5170000 KHz - 5250000 KHz @ 40000 KHz), (300 mBi, 2000 mBm)
[22291.352017] cfg80211:   (5735000 KHz - 5835000 KHz @ 40000 KHz), (300 mBi, 2000 mBm)
[22306.450438] IPv6: ADDRCONF(NETDEV_UP): wlan0: link is not ready

The same for syslog:
Nov 18 15:35:17 ian-Latitude-E6420 NetworkManager[1067]: <warn> Activation (wlan0/wireless): association took too long, failing activation.
Nov 18 15:35:17 ian-Latitude-E6420 NetworkManager[1067]: <info> (wlan0): device state change: config -> failed (reason 'SSID not found') [50 120 53]
Nov 18 15:35:17 ian-Latitude-E6420 NetworkManager[1067]: <info> NetworkManager state is now DISCONNECTED
Nov 18 15:35:17 ian-Latitude-E6420 NetworkManager[1067]: <info> Marking connection 'Auto BTHub3-35MZ' invalid.
Nov 18 15:35:17 ian-Latitude-E6420 NetworkManager[1067]: <warn> Activation (wlan0) failed for connection 'Auto BTHub3-35MZ'
Nov 18 15:35:17 ian-Latitude-E6420 NetworkManager[1067]: <info> (wlan0): device state change: failed -> disconnected (reason 'none') [120 30 0]
Nov 18 15:35:17 ian-Latitude-E6420 NetworkManager[1067]: <info> (wlan0): deactivating device (reason 'none') [0]
Nov 18 15:35:17 ian-Latitude-E6420 NetworkManager[1067]: <info> (wlan0): supplicant interface state: scanning -> disconnected
Nov 18 15:35:17 ian-Latitude-E6420 NetworkManager[1067]: <warn> Couldn't disconnect supplicant interface: This interface is not connected.

I've tried the "nmcli nm sleep false" but it doesn't work for me, I don't see a "sleep" option:
$ nmcli nm
RUNNING         STATE           WIFI-HARDWARE   WIFI       WWAN-HARDWARE   WWAN      
running         disconnected    enabled         enabled    enabled         disabled 
$ sudo nmcli nm sleep false
Error in sleep: Already awake
and forcing it to sleep says that it is already awake.