Happens to me more than I'd like usually if I try to do something to fast, maybe before RB is finished doing the first thing.

Learned to never click "Recover data from previous session".
Just go to File> Open Recent and hope I saved often.

Also get an Error Message sometimes when hitting Save which says something about "Can't save that file type or some such"

Then I have to Save As and just overwrite the existing open file.
Weird!

Speaking of which, every once and awhile my sound shuts off and I have to restart the computer to get it back.
Any suggestions as to why?