B43 Wireless not working on 2.6.35 kernel

By default when you upgrade from one release to another, all of the proprietary drivers are disabled. You need to use the 'Hardware Drivers' application to reenable them.

Try installing the one from the Broadcom website. It's here. Follow the instructions in the readme.

Alternatively, try reinstalling the driver, it worked for me once.

Neither reinstalling the firmware from the command line nor building the driver from source provided by Broadcom in @evgeny 's link worked for me when I had the same problem with my Compaq Presario V5000 with the B43 3418 chipset.

But using ndiswrapper did work. (I used the ndisgtk GUI and this driver)