I installed Mythbuntu 8.04 on a P4 2.4GHz Gateway motherboard (with Hauppage PVR-350) and I've gotten most of it to work.
WakeOnACPI works almost. I followed the direction on the page "WhatNext/ACPIWake" (or something like that) and it turns the computer on and off. However, I scheduled a recording one night at 8pm (Daily Show) for half an hour and it ran and then turned itself off. Now it wakes up every night at 8pm and starts the frontend ( even though I've set it up for MythWelcome) which means it doesn't shutdown automatically.

Any idea what could be wrong?