What about the software you might be running? Sometimes the odd app can have strange effects on windows.
You could also try running the system file checker. Open an admin command prompt and type:
sfc /scannow
Press enter and await results.
If you get corrupt files which cannot be repaired try running this command (again in admin command prompt), type:
DISM /Online /Cleanup-Image /RestoreHealth
Press enter and await results. Be patient as it can take some time.