I actually have the same board,
My issue is similair but under vista, Paranoid Delusion recommend I made separate thread. From a other client (also laptop) Tv works ok. (also with the occasional hiccup but I'm guessing thats because of wireless connection having too little bandwidth) From mediaportal on the same pc mediaportal crashes as opposed to your cause where the whole pc crashes.
Turning tv on crashes mediaportal
*edit
UPDATE!: if I disable crossfire (and thus the onboard HD3200) it works. I don't know if you have a separate videocard around so you could verify that this can be traced back to the onboard card.