I don't know this board, but I know that it's not uncommon in the Ghosts for the switched jacks to go flaky and cause troubles. The headphone output is often the culprit in those, but mine also had problems with some of the insert jacks. If those switch contacts get oxidized, and stop making a good connection, it interrupts the signal, and things will get "flaky" and/or go dead. It almost sometimes seems to help to goose the gain and slam a huge signal though, but that's not a fix. They're supposed to be self-cleaning, but that only works if you're actually plugging and unplugging fairly regularly.
It's probably too much to hope that this is your problem, but it's something to investigate, and a relatively easy fix.