System sleeping after delay

[TrevorBradley]

I have a problem with my mythbuntu frontend. After a certain amount of time (perhaps half an hour?) the display goes offline and the system appears to be semi-unresponsive. I'm unable to wake the system with the remote, or with the keyboard (spacebar), though I am able to wake it with Ctrl-Alt-F5, Ctrl-Alt-F7 (switching on and off X windows).

I've had a good look through xorg.conf, and the system settings, and while I believe the system isn't going to screensaver, it's behaving in an odd way. I believe I can ssh into the system when it's in this state (about 90% certain of this, it's been a while since I've tested this).

I was wondering if anyone could suggest an avenue of investigation as to what might be wrong with my system?

EDIT: I'm running Jaunty on an Asus M2NPV-VM motherboard

EDIT2: One other thing likely of relevance. I believe the problem doesn't occur unless you either watch recordings or video. I've left mythbuntu at the root user interface and the display doesn't turn off. Could it be related to mythvideo?

Thanks in advance! Apologies if I don't have enough information, having to wait hours to adequately test this make it difficult to get proper data.