user gets logged out by itself

If I leave my computer on for a while it logs my user out, or tries to.

Often I come back and several apps have been quit out of and there is a message telling me that one of my apps stopped my user from being logged out.

Other times it is logged out and I have to log back in and start from scratch.

Seems similar to https://discussions.apple.com/thread/4135972?start=0&tstart=0 but I am not running multiple graphics cards and as long as I am working on the computer it has never happend. It only happens if I leave it running for a while not uning it.