Should have checked Sheldon's site first but it was a rapid response requirement. Her hub was locking up without braking. She does like to lay down the skids though so maybe she caused the problem.

Anyway I went in there and took it all apart and greased things and managed to get it back together and working - didn't appear to be anything broken but it wasn't anything like I had imagined it would look like. Also, I thought the "reaction arm" was just a wheel retention device for dummies - but since I couldn't get it off I didn't do anything stupid.