Problem description:
After playing the game for a while the complete system hangs untill I reset the computer. I'm not doing anything specific at that moment, so it's hard to reproduce. The game doesn't slow down before the hanging. The only way to prevent it from happening is saving the game every few minutes. Possibly related: When I run any other program at the same time (like eMule in Wine or Amarok), the game stutters heavily.
I haven't had the fan on my GPU fail before. But is there a utility to monitor GPU heat for Linux? I don't think it's the problem however, since I've been playing this game for hours on end and as long as I keep saving all the time nothing happens, only when I forget to save for a while the system hangs. So unless saving the game restarts my fan (highly unlikely), it's not related.
Well, what I thought is that maybe saving the game makes you enter the menu, which could reduce the system load and thus the temperature. But probably you are right and this is not the case.
I have absolutely no explanation for this and no one else has ever experienced it as far as I can remember.