Is there any freeware programs to delete hidden popups?

when i close down windows or log off a box appears with nothing inside it but on the top of the box it says exactly (UIhiddenpopup) iv'e tried spybot/ adaware/ spyware vanisher/ windows defender/ my antivirus program even tried different popup killers but does not get rid of it. and not only that it loads in the backround you can't see anythink. i would be gratfull if any one can help