Atualizei o kernel novamente, e o problema persiste.
uname -a
Linux FPMG 3.15.0-031500rc1-generic #201404131835 SMP Sun Apr 13 22:36:23 UTC 2014 x86_64 x86_64 x86_64 GNU/Linux
$ iwconfig
wlan0 IEEE 802.11bgn ESSID:"PL_HOME_BR"
Mode:Managed Frequency:2.412 GHz Access Point: 2EF
Bit Rate=144.4 Mb/s Tx-Power=16 dBm
Retry short limit:7 RTS thr:off Fragment thr:off
Encryption key:off
Power Management:on
Link Quality=49/70 Signal level=-61 dBm
Rx invalid nwid:0 Rx invalid crypt:0 Rx invalid frag:0
Tx excessive retries:0 Invalid misc:846 Missed beacon:0
Saída do kernel log
Apr 14 09:37:24 FPMG kernel: [ 3607.982925] wlan0: RX AssocResp from 20:ef (capab=0x411 status=0 aid=3)
Apr 14 09:37:24 FPMG kernel: [ 3607.986149] wlan0: associated
Apr 14 09:45:00 FPMG kernel: [ 4063.763408] wlan0: deauthenticating from 20:a::ef by local choice (Reason: 3=DEAUTH_LEAVING)
Apr 14 09:45:00 FPMG kernel: [ 4063.772891] iwlwifi 0000:08:00.0: Drained sta 0, but it is internal?
Apr 14 09:45:00 FPMG kernel: [ 4063.775518] cfg80211: Calling CRDA to update world regulatory domain
Apr 14 09:45:00 FPMG kernel: [ 4063.779366] cfg80211: World regulatory domain updated:
Apr 14 09:45:00 FPMG kernel: [ 4063.779372] cfg80211: DFS Master region: unset
Apr 14 09:45:00 FPMG kernel: [ 4063.779373] cfg80211: (start_freq - end_freq @ bandwidth), (max_antenna_gain, max_eirp), (dfs_cac_time)
Apr 14 09:45:00 FPMG kernel: [ 4063.779375] cfg80211: (2402000 KHz - 2472000 KHz @ 40000 KHz), (300 mBi, 2000 mBm), (N/A)
Apr 14 09:45:00 FPMG kernel: [ 4063.779377] cfg80211: (2457000 KHz - 2482000 KHz @ 40000 KHz), (300 mBi, 2000 mBm), (N/A)
Apr 14 09:45:00 FPMG kernel: [ 4063.779378] cfg80211: (2474000 KHz - 2494000 KHz @ 20000 KHz), (300 mBi, 2000 mBm), (N/A)
Apr 14 09:45:00 FPMG kernel: [ 4063.779380] cfg80211: (5170000 KHz - 5250000 KHz @ 40000 KHz), (300 mBi, 2000 mBm), (N/A)
Apr 14 09:45:00 FPMG kernel: [ 4063.779381] cfg80211: (5735000 KHz - 5835000 KHz @ 40000 KHz), (300 mBi, 2000 mBm), (N/A)
Apr 14 09:45:00 FPMG kernel: [ 4063.994724] r8169 0000:07:00.0 eth0: link down
Apr 14 09:45:00 FPMG kernel: [ 4063.994794] IPv6: ADDRCONF(NETDEV_UP): eth0: link is not ready
Apr 14 09:45:00 FPMG kernel: [ 4063.996813] iwlwifi 0000:08:00.0: L1 Enabled; Disabling L0S
Apr 14 09:45:00 FPMG kernel: [ 4063.997047] iwlwifi 0000:08:00.0: L1 Enabled; Disabling L0S
Apr 14 09:45:00 FPMG kernel: [ 4064.008514] IPv6: ADDRCONF(NETDEV_UP): wlan0: link is not ready
Apr 14 09:45:02 FPMG kernel: [ 4065.776102] wlan0: authenticate with 20:a:4b:b4:89:ef
Apr 14 09:45:02 FPMG kernel: [ 4065.780497] wlan0: send auth to 20:a:ef (try 1/3)
Apr 14 09:45:02 FPMG kernel: [ 4065.900565] wlan0: send auth to 20:a::ef (try 2/3)
Apr 14 09:45:02 FPMG kernel: [ 4065.908691] wlan0: authenticated
Apr 14 09:45:02 FPMG kernel: [ 4065.911546] wlan0: associate with 20::89:ef (try 1/3)
Apr 14 09:45:02 FPMG kernel: [ 4065.915567] wlan0: RX AssocResp from 20a:4b:b4:89:ef (capab=0x411 status=0 aid=3)
Apr 14 09:45:02 FPMG kernel: [ 4065.918009] wlan0: associated
Apr 14 09:45:02 FPMG kernel: [ 4065.918040] IPv6: ADDRCONF(NETDEV_CHANGE): wlan0: link becomes ready