Please read this (reposting) from Joao in Portugal:
https://discussions.apple.com/thread/3394498?tstart=0 and
http://rys.pixeltards.com/2011/09/04/osx-lion-wifi.html
Apple will not confirm if you call them! Nor did my ISP!
You have the affected chipset. See, my MacBook shows a Broadcom set and IO80211 family 3.2. The bad one should read Atheros (which you have) and IO80211 family 4.0.x (which is from Lion) or so. That combo is affected, somehow. In my case disabling N-Band in the WiFi router itself remedies the problem, can't tell you why.
Software Versions:
Menu Extra: 6.2.2 (622.2)
configd plug-in: 6.2.5 (625.6)
System Profiler: 6.0.1 (601.1)
Network Preference: 6.2.2 (622.2)
AirPort Utility: 5.5.3 (553.20)
IO80211 Family: 3.2 (320.1)
Interfaces:
en1:
Card Type: AirPort Extreme (0x14E4, 0xD6)
Firmware Version: Broadcom BCM43xx 1.0 5.100.198.104.5)
Locale: ETSI
Country Code: NL
Supported PHY Modes: 802.11 a/b/g/n
Supported Channels: 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 36, 40, 44, 48, 52, 56, 60, 64, 100, 104, 108, 112, 116, 120, 124, 128, 132, 136, 140
Wake On Wireless: Supported
Status: Connected
Current Network Information:
Do you have IO80211 family 4, then read the linked files, and see if you want to try. The rest of my Mac is fine, but this issue is indeed horrible. Best of luck!