Hi Libra,
This isn't a great answer - I had the same on two separate machines running Win 8.1 which happened at different times (a month or two apart) but seemed to occur after a windows update. Unfortunately I didn't have Win restore set up correctly so had no restore point to go back to.... only thing I could do was a re-build.
All I can suggest is that you go into system restore and see how far back you have restore points and try one before your problems occurred. Finally if that doesn't work use the search facility in Win and type in 'Update & Recovery' and select 'Remove everything & re-install windows' - Take a backup of your files first as it will flatten your machine and your data will be wiped clean.