If you leave diablo 3 open at the select hero screen and then you put your computer to sleep (for more than a few minutes) when you go to the game again you can't create a game (obvious because connection was lost) but if you hit logout then the game freezes and the only way to get out of it is to ctr+alt+del and terminate the app.

running on a i7-2600k, nvidia 680gtx, 8gb ram