There is a new issue that your files will suddenly not be able to open them and that states the file is encrypted.
You maybe infected with a ransomeware virus like Cyptowall or Cyptolocker.
Check for the presentce of a file called something like this:
"HELP_YOUR_FILES.PNG"
This will explain what has happened to your files and that they have been encrypted by the virus.
See sample here:
https://copy.com/EAEzMXRNW49jvT6q
