I have the same problem but with an additional twist. I have no desktop icons or task bar, just the wallpaper. Right clicking on the desktop or CTR+ALT+DEL get no response. In addition, the system automatically logs me off after a minute or 2 no matter what account I log in under. All of this happens even if I try booting into safe mode.
I connected to the C: drive from another PC and all of my desktop folders, icons, etc. are in the 'desktop' folder so they are not wiped out. I ran a virus scan of the C: drive from the other computer using McAfee but it didn't find anything. Also tried copying the explorer.exe file from my good PC but that also had no affect. All of my documents, favorites, etc. are on a NAS drive so they are OK.
Before I wipe and reinstall the system, anybody have any suggestions?