I had the same problem, i did everything i read in forums but nothing happened...
The first time i solved this problem i had to delete my user's profile completely and had windows to recreate it... it worked fine
Eventualy (i'm talking about 2 or 3 days), the f***ing rectangles came back and this time really pissed my off 'couse i went through hell reconfiguring all my profile. I downloaded Dial-a-Fix and it encountered with a problem... i changed this registry value to 0, restarted and it worked
HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Policies\Explorer\ForceActiveDesktopOn
Hope it helps.
