I've had this happen to me without hardware issues. The game ended up getting corrupted with an update, and sort of just deleted itself, as far as Steam could tell.
Checking the drive, the files and all that were still there. I just hit install and it basically verified game files and redownloaded the shit that broke.
Though I don't believe a software corruption like that is very common, so odds are, you're looking at some kind of physical issue with your computer. Likely RAM or your hard drive. Try reseating your RAM, and doing a SMART check of your drive.