I have the same situation, would really like to know if there is a fix for this !
I have actually taken the unit apart and found an SD card inside (4Gb Transcend) which if I plug into my computer does not register at all as if it is dead
I tried booting the unit without the SD card and I get a black screen telling me to take the unit to a Pioneer service center, put the SD card back in and and it goes back to trying to start and the constant rebooting thing. I suspect the SD card is faulty or corrupted but I have no way to know