Currently Being ModeratedMay 6, 2013 9:53 AM (in response to Rockgoose)
Some Internet service providers use a method called "hardware access provisioning" to regulate access to their networks.
AirPort Base Station: ISP provisioning may prevent Internet connection via broadband (cable or DSL)
If that doesnt work take a look at:
Troubleshooting Wi-Fi issues in OS X Lion and Mac OS X v10.6
Hope this helps,