I share jomage's pain. I am in the same situation as you. I've looked everywhere for such problem to no avail, then I got my hands dirty and went looking for the root of the evil. I found it (I think), but can't fix it (I'm sure). jomage, start your pc on battery, let it hang, restart the pc with ac power and go check the system logs. Is there any message regarding acpiec at time on the system's hang? If so, we have the same problem. I've upgraded the bios, but it is the same.