WiFi update 10.7.3
Apple DNS Servers:
Move the Base Station If interference is particularly bad in one part of your house or office, move the base station to another location. But this can be tricky if your AirPort base station has to connect to the broadband feed coming into the house and that feed happens to enter at a particularly interference-prone spot.
Use the 5GHz Band Compared with the 2.4GHz band, the 5GHz band is practically empty. The newest AirPort Extreme Base Station is one of the few Wi-Fi base stations designed for home use that work in that 5GHz band. All of Apple’s Core 2 Duo laptops and iMacs (except the discontinued 17-inch 1.87GHz model) can also use the 5GHz band; with the build-to-order wireless option, so can the Mac Pro.
To switch to the 5GHz band, launch AirPort Utility, select your base station, and switch to Manual Setup. Click on the AirPort button and select the Wireless tab. Select 802.11n Only (5 GHz) from the Radio Mode pop-up menu. Click on the Wireless Options button and select Use Wide Channels. Click on Update to restart the base station.
Currently, no Mac-compatible adapters enable you to use the 5GHz band in older Macs or with older versions of OS X.
These Firmware updates may or may not apply to your system, but may help with your particular problem.