Avast suggested you open a game in safe mode?
Strange, as that would prevent Avast from running in the first place.
Are you sure the save files were lost? Do you know where to look for them? They might have been corrupted by the crash (I’d check for game updates or video card driver updates to fix that), but if they really were deleted, I’d suggest a recovery tool like http://www.piriform.com/recuva