Latest Broadcom Drivers Fix Windows 7 WiFi Problems
Several users have reported a problem in which Windows 7 RC1 systems either cannot connect to wireless networks or display the message low connectivity or no connection when attempted to the network. In some cases, using Windows 7′s built-in “fix” routine can resolve the issue, albeit temporarily.
Updating to the latest set of Broadcom wireless drivers, for systems that use Broadcom chipsets, resolves this issue for most users. In particular, users have had success with driver version 126.96.36.199, available here.
You may also want to run Windows Update to check for the latest drivers for wireless hardware from other manufacturers.