I'd expect you to get some kind of error message such as a time out or such. Have you noticed if it happens in the same place or does it appear to be random? If it is always in the same place, could be some kind of graphical glitch or a feature you have selected in settings that your hardware either doesn't support or has trouble with. I'd make sure your drivers are up to date, especially sound and graphics above all. Also, try kicking all the graphic options to their bare minimum and see if that gets you through (assuming updating drivers doesn't help) I really am going to have to go against it being the client as it should have been caught by error handling and spit out some kind of message. To me, sounds like Windows is terminating it for some reason.