hey man, I had the EXACT same thing happen to my system. I wasn't getting any power to the back of my headunit all of a sudden. I couldn't tell you what to do because this happened to me a week ago and i still haven't found out what was wrong. And with the amp, i fried it. I actually took it apart and 3 of the transistors were blown along with the actual board. I don't know if this is your problem but you might want to check to see if you are still getting juice to the back of the headunit. Just a thought. Hope this might help.
Josh

winter project: custom t3/t4 turbo and some others