When the power goes out on everything, check the voltages out of your bridges for output, if nothing then check input, if that is good then you may have a bad bridge. Check them out (there is a thread about how to do that including a youtube).
If the bridges have output, check your PS for 6.3V output to the the GI relay. If you have that then your GI may have shut down because your MPU is blanking the Driver Board (pinwiki shows how to check that).
Also when this happens do you have any indicators on at all on the MPU? If no then your really looking at a PS issue.
Basically what you are looking at while it seems like a lot, is probably just a bad 40 pin connector stopping the driver from working.
Lots easier to troubleshot that an intermittent that only resets the game every other day.