it seems that there is a problem with the Patch3, mcafee block explorer.exe at startup windows and you cannot see the desktop
if you have this problem :
Click Start => Programs =>McAfee => VirusScan Console
push right-click on Access protection and select Properties.
choose anti-virus standard protection.
choose prevent Windows process spoofing => deselect the Block option.
you can disable too report option.
push OK
and now mcafee doesn't block anymore explorer.exe