Just come across this post although its well over a year old.
I have a similar problem with my Duoverb head. It just froze one day last year. Now only the pilot light comes on. No sound whatsoever from the amp. Left it in the garage for 18 months. Nobody could help and line 6 are the worst amp company I have known for after sales service. I will NEVER EVER buy new line 6 stuff again. They say you have to go to authorised dealers for repair!! Nearest one 0ver 200 miles away. When I rang them they never even heard of a Duoverb!! "Must be an old one" they said, and thats an authorised dealer who put me off further by stating "doubt we could get parts for it"
This weekend I tried it agan, same problem, just the pilot light and no other lights and no sound. Then I tried switching off and on holding down preset D switch. I actually then got sound!! But just a basic flat response amp sound that does not respond to any tone or volume or split or combine switches. Only the master volume. About the same volume as a small practice amp!! Something not well with it at all!
I cant find anybody who will touch the thing or knows what to do, not even line 6!!
bIding my time now hoping to pick up broken duoverbs and change the pcb's over