I'm not going to give work arounds.I guess you have already tried gpedit.msc and security stuffs.
DownloadWindows repair tool
Extract and launch the Repair_Windows.exe
Click on Start repairs
tab-click on Start
check mark following options alone
Reset registry permissions
reset file permissions
Checkmark Restart System When Finished
click the Start
System should restart after repair
Let me know if that helps
Does it happen on IE? Did you download files from other browser like firefox?
Edited by narenxp, 19 September 2012 - 09:43 AM.