Hello. I am having a similar type of problem with Windows 7 64 version. If I go into my computer and try to access the c drive there is no response. I can usually access most other things in windows explorer after first booting up, but after a while nothing shows up in windows explorer. Also, I can't shut down.
This problem first seemed to start after I tried installing MagicDisc (Virtual drive software) but shortly after the computer froze. This problem has been present ever since.
Other programs I am using include
AVG (virus software)
Software and downloaded drivers for a Creative sound card (I had to download 64 bit drivers and the install wasn't the cleanest, but I didn't notice any problems resulting immediately after this.)
Linksys Wireless Network Manager (I also had to download some rather unofficial drivers as linksys does not seem to provide 64 bit drivers for their product)
Firefox
Nvidia drivers (They installed very cleanly and seemed to even be designed for windows 7, so I doubt they were the cause)
I have tried to uninstall MagicDisc but this hasn't helped. I'm not sure if it is because of another cause or because what I did had not undone the damage. Eskimo, did you have this problem initially or after installing a few programs?