I been treated to a frequent but erratic occurrence of this bug:
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iwlagn 0000:05:00.0: Microcode SW error detected.  Restarting 0x2000000
Registered led device: iwl-phy0::radio
Registered led device: iwl-phy0::assoc
Registered led device: iwl-phy0::RX
Registered led device: iwl-phy0::TX
iwlagn 0000:05:00.0: Stopping AGG while state not ON or starting
iwlagn 0000:05:00.0: queue number out of range: 0, must be 10 to 19
WARNING: at /build/buildd/linux-2.6.32/net/mac80211/agg-tx.c:150 ___ieee80211_stop_tx_ba_session+0x82/0x90 [mac80211]()
Hardware name: VGN-FW140E
Modules linked in: cryptd aes_x86_64 aes_generic ppdev vboxnetadp vboxnetflt vboxdrv snd_hda_codec_intelhdmi snd_hda_codec_realtek snd_hda_intel snd_hda_codec snd_hwdep fbcon snd_pcm_oss snd_mixer_oss tileblit snd_pcm font snd_seq_dummy snd_seq_oss bitblit snd_seq_midi softcursor snd_rawmidi vga16fb snd_seq_midi_event vgastate arc4 snd_seq snd_timer uvcvideo videodev iwlagn snd_seq_device v4l1_compat i915 iwlcore btusb usbhid drm_kms_helper snd v4l2_compat_ioctl32 bluetooth joydev sdhci_pci hid mac80211 soundcore sdhci drm psmouse cfg80211 snd_page_alloc serio_raw led_class i2c_algo_bit sony_laptop intel_agp wacom lp parport coretemp video output usb_storage ohci1394 ahci sky2 ieee1394 [last unloaded: kvm]
Pid: 9, comm: events/0 Not tainted 2.6.32-24-generic #42-Ubuntu
Call Trace:
[<ffffffff81066dbb>] warn_slowpath_common+0x7b/0xc0
[<ffffffff81066e14>] warn_slowpath_null+0x14/0x20
[<ffffffffa015b922>] ___ieee80211_stop_tx_ba_session+0x82/0x90 [mac80211]
[<ffffffffa015babf>] __ieee80211_stop_tx_ba_session+0x7f/0x90 [mac80211]
[<ffffffffa015b267>] ieee80211_sta_tear_down_BA_sessions+0x27/0x50 [mac80211]
[<ffffffffa01701a8>] ieee80211_reconfig+0x378/0x460 [mac80211]
[<ffffffffa01564c0>] ? ieee80211_restart_work+0x0/0x30 [mac80211]
[<ffffffffa01564e2>] ieee80211_restart_work+0x22/0x30 [mac80211]
[<ffffffff81080867>] run_workqueue+0xc7/0x1a0
[<ffffffff810809e3>] worker_thread+0xa3/0x110
[<ffffffff81085430>] ? autoremove_wake_function+0x0/0x40
[<ffffffff81080940>] ? worker_thread+0x0/0x110
[<ffffffff810850b6>] kthread+0x96/0xa0
[<ffffffff810141ea>] child_rip+0xa/0x20
[<ffffffff81085020>] ? kthread+0x0/0xa0
[<ffffffff810141e0>] ? child_rip+0x0/0x20
 ---[ end trace a69e8e33c007fa40 ]---
wlan0: deauthenticated from d8:5d:4c:b9:f4:ba (Reason: 2)
wlan0: direct probe to AP d8:5d:4c:b9:f4:ba (try 1)
wlan0: direct probe responded
wlan0: authenticate with AP d8:5d:4c:b9:f4:ba (try 1)
wlan0: authenticated
wlan0: associate with AP d8:5d:4c:b9:f4:ba (try 1)
wlan0: RX AssocResp from d8:5d:4c:b9:f4:ba (capab=0x431 status=0 aid=1)
wlan0: associated
CE: hpet increasing min_delta_ns to 15000 nsec
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I am running the 64bit Kubuntu 10.4 with KDE 4.5 and with this kernel:
2.6.32-24-generic #42-Ubuntu SMP Fri Aug 20 14:21:58 UTC 2010 x86_64 GNU/Linux
on my Sony VAIO VGN-FW140E, which has the 
"Intel Corporation Wireless WiFi Link 5100" wireless controller.

It characterizes its appearance by 
1) blinking my cable modem lights as if it was going through a power cycle, and 
2) overwriting my ISP's DNS and domain name in resolv.conf with my wireless router gateway address: 192.168.1.1.  

Pinging google.com returns nothing.

I used to power cycle my wireless and modem but I found that IF I manually restore /etc/resolv.conf from my backup copy the wireless connection will automatically resume and after a minute or so I can get a response from pinging google.com, and I can then continue browsing.  That led me to adding my IPS DNS and domain name in the DHCP configuration section of my wireless router.  Now, when my connection drops and automatically restores, my wireless router restores /etc/resolv.conf and after a few seconds I can continue browsing.