This happened in my 2007 4.8 for a bit. I dropped it at the dealer and when I picked it up, they said they had to reprogram the radio unit. With that said, my symptoms were similar to yours, except not. Once in a while, I'd just lose radio period. No chime/ding, nothing. The screen worked, and I could select CD/AUX/SAT but no FM nor AM showed in the list. Odd, right? So, the next day after that would happen, everything would work and be fine. This was over a year ago and I haven't had an issue since.