I had same problem under windows 10 x64
Tried scf/scannow but no results, the below link solved the problem(although SCF showed corrupted files)
1. Go to start and type regedit.exe.
2. Navigate to the following location: HKEY_CURRENT_USER\Control Panel\Desktop.
3. Double click the 'ForegroundLockTimeout' key. Change the notation to decimal.
4. The default value should be 200000 millisecond in decimal, or 200 seconds. Click OK.
5. Restart your computer and check if the issue persists.