Right, let's try something...
1, Click Start > All Programs > Accessories
and right-click Command Prompt
then Run as Administrator
2, type sfc /scannow
This will run a system file integrity check which will check to see if your system files are all ok, any changes made will be fixed and a reboot required.
If that reports no issues then you may want to try Repair Install
It will not affect any user files or programs installed