I have exactly the same problem on my HT-BD1250, latest firmware. I did not find any threads on your message and was wondering if and how your problem was solved. Thanks.
My HT -Z320 Home Theater wont turn on. When I press ON on unit or remote unit turns on briefly displaying in sequence HELLO - D-IN - PROT and then the unit turns off. Same if y press OPEN or any other function. Always end in PROT and turns off. What does PROT mean and how can I keep unit ON? thanks