Error code 38 on entering cash shop

I doubt any of those things are relevant, since this one character d/cs on *every* computer I've tried, while other characters, even on the same account, work just fine on every computer.

I guess this response they gave you is their standard "We have no bleeping idea what's causing that malfunction. Try turning off and on and slapping it a bit, maybe that'll jiggle it to work". Very encouraging.