The API on my Twitter Account seems to be BORK'd

The API on my Twitter account (BenPaddon) has been broken for, ooh, three months now? I've had a Twitter Support ticket for the last two which ahs gone largely unnoticed. Using clients such as Twhirl, Twitterrific and so on will, nine times out of ten, return a "Bad Request" message. Sometimes it works, but it's intermittent and unreliable. This also affects the "Twitter Tools" plug-in on my blogs.

I'm fairly certain it's my account specifically, because I have a couple of other accounts that work fine.