Could be your anti-virus not accepting this program all of a sudden.

Could be your Cache is not cleared and too much is in open RAM. To do the latter go to File Explorer, then to This PC. Then to Local disk (C:) <-- if that's your hard drive, Right Click on Local Disk (C:) and click on Properties. Click on Disk Cleanup and check every box in the list. Finally click Ok.  It may work immediately if this is your problem, or it may take one more reboot.