Recently worked on a Dell Inspiron 1525 that couldn't see any available wireless networks. It had a switch on the side called a "WiFi Catcher", and the WiFi Catcher would show the wireless networks, but not allow you to connect to them.
The Dell Wireless Utility would throw the following error when opened, "The wireless network adapter could not be accessed. This application may have diminished functionality as a result."
When you opened the Windows wireless "Connect to network" window, the dropdown box next to "Show" at the top was empty and no wireless networks would show up.
Researching the issue, there was everything from checking the WLAN AutoConfig service to a Vista Service pack update causing the problem, but trying everything encountered in research didn't seem to resolve the issue.
So, we ran system file checker (SFC /scannow) from an elevated command prompt. SFC indicated corrupt system files that it couldn't repair, check the CBS.log file at C:\windows\logs\CBS\CBS.log.
When I checked the log file, it indicated 3 files that it was trying to restore, but the source file was also corrupt. The 3 files were:
Hmmmm... these all seem to look like they are related to my problem.
To resolve the issue, I went to a WORKING Vista computer, copied the above files to a flash drive, renamed the old corrupt files on the NON-working Vista computer (the Inspiron) so I had a backup, and then copied the files from the flash drive to the proper location and rebooted.
Viola! Wireless networks now seen in the "View available wireless networks" dialog box!