I have the same problem. I had it looked at by a very reputable authorized repair depot and they also contacted Line 6 via email and copied me on the chain. Basically no solution. Very disappointing lack of support for what I understand to be a common problem. No replacement parts available. They did say you can try to have a service tech "re-flow" the solder on the DSP board but no one is willing to do it that I can find. I have other Line 6 gear but ths puts a bad taste in my mouth for any future purchases from Line 6. Too bad.
Rick