Quote Originally Posted by ChrisBCritter
Did you accidently trip the manual switch for the wireless? There should be an external switch for it somewhere on the perimeter of the laptop.
Either this or Windows Update could have grabbed you a new wireless driver if you allow automatic updates or something.

You can either try uninstalling the wireless device through control panel/system/device manager and reboot, or just roll back the driver, or use system restore to go back to whenever you know it was working for sure.