I had a similar issue when I turned on my laptop today. My wireless adapter had been working fine up until then. This morning, my list of available wifi networks was empty and it just said no networks available. I tried the obvious things like recycling the adapter, running the troubleshooter, and reinstalling the drivers and none of these helped. The only thing that had changed overnight is that I had installed the latest set of windows updates. To check if one of these had corrupted my system, I did a system restore back to the latest restore point (done at around 5pm yesterday). That fixed my problem and I can now see all my networks again. I cannot tell you which specific windows update corrupted my system but its something else you might consider if your system was previously working fine like mine was.