1. System will lockup after watching live T.V for a period of time
2. System will not lock on to a channel and shows no signal. If the system is restarted chances are it will work O.K second time around.
1) try adding a fan onto the CPU HSF - even if it's temporary, then it will prove one way or the other if it is heat related.
2) is this when the pc comes out of standby/sleep? alot of tv cards use the v4l framework, and that doesnt appear to like resuming from sleep states (other than full restarts/startups). unloading your TV card drivers via 'modprobe -r' before sleep, and then modprobing them on resume fixes it.