It is a general error message that is given when the document is corrupting
and the fault isn't identified. My guess is that maybe your username temp
folder is full of abandoned temp files and needs emptying. The Temp folder
should be empty when all applications are closed. So after a fresh reboot
and before you open any apps, navigate to your temp folder (location depends
on OS) and delete everything you find in there. If you have not done this
recently, don't be surprised if there are thousands of abandoned temp files
in there.