THat is indeed unusual behavior from a major appliance.
Hmmm... first I suggest less punctuation
The fact that the HU won't change sources rules out having the amp be the problem.
We had an odd problem in an E39 that ended up being a bad iPod interface. Does the video interface you used tie into the databus? If it went bad it might disable things.
I think you are on the right track - the interface being removed is the first thing I would test.