It wouldn't surprise me if TrainerFu is broken or was a ton of quirks. It's a horrible, outdated mess and really ought to be rewritten from scratch as a shiny new LDB plugin. Unfortunately I have no clue how to do that, and noone else seems interested.
Tried switching to JWowUpdater and when it reinstalled my addons it didn't pick up the Babble-Trainer-2.2 dependency. After installing Babble-2.2 manually it works fine, but it seems silly to have to install both Babble-2.2 and LibBabble-whatever-3.0 to make one addon work.
Does anyone know of any alternatives to TrainerFu? It's such a mess now and probably won't work well with WotLK anyways.
1. Exit out of the game
2. Open up your World of Warcraft\WTF\<accountname>\SavedVariables folder
3. Delete FuBar_TrainerFu.lua and FuBar_TrainerFu.bak
4. Re-enter the game and re-visit all your trainers
This cleared up all my issues, but made me lose all my trainer data on all my toons until I re-visited them.
Okay I'm reverting TrainerFu to r56106. Once you pull down the updated version, you may need to wipe your data and visit trainers again to get things back in order.
Edit: I dunno, both versions seem to have problems with Bolt of Silk (Cloth?) and Enchant Gloves - Greater Agility for me. I wish someone who knew about this addon would take a damn look at the bugs because I don't know what the hell to do.