It's a display issue that causes this blank screen when actually the software is till running on the PC. Somehow the installation has become corrupted.
Please uninstall your McAfee product in the normal manner (Control Panel/Programs/Uninstall a Program in Vista/Windows 7 or Add or Remove Programs in XP) then run the removal tool from here : http://service.mcafee.com/faqdocument.aspx?id=TS100507
Reboot and reinstall the latest version from the online account and everything should be fine.
Could you please confirm if you still have the issues persisting ???