Comment 2 for bug 382531

Same problem here. Dell Vostro 1520, for what it's worth, but I don't think this is a hardware issue.

For whatever reason, the OS seems to think the computer is idle when I am playing a game. Eventually the screen will dim, the screensaver will activate and then I lose most control of keyboard and mouse functions. I can Ctrl+Alt+F1 to get a terminal so I can reboot but from terminal 7 (x server) I get no keyboard or mouse response. The game is still running though.

Jaunty, repository install, full screen mode as well.