It's not a fuse. Most likely the culprit is the data bus wire between the face and the unit. Only way to fix it is to send to a repair center, or pioneer if it's still under warranty.
if it makes you feel any better, I've always had problems with pioneer's 8400, 8500, and Premier 840, 850, as a vendor because of warranty issues. Poor design. It happens. This year Pioneer recalled the DEH 1600, last year it was their entire amp line up. That's just the world of electronics, as eve my 7015 acts up every now and then.