I had the same thing happen to me. Gale couldnt talk to anyone, and nobody could interact with Gale. Luckily I was only a few quicksaves away from when it happened, and I was able to revert it. It happened during combat with the tollmaster, in the shadowed lands. One of the skulls used a silencing spell on Gale, and even though the status effect was gone, it still seemed to affect him.
