I logged back into the server I've been playing on this morning, and the MCA setup screen came up, with no buttons.
http://i.imgur.com/z9lK4dx.png
A few minutes later I got this crash: http://pastebin.com/1mz013X9
My player data has been reset on the server, but I am still getting the same crash/problem every time I join.
I still get the problem after reinstalling.

Has the server reinstalled MCA? It must be downloaded again, as a silent update fixed this issue a while ago.

This happened with the updated version I think (the one uploaded on 22/02/2014)
Deleting the config for my player on the server for MCA fixed the issue for now.

That is most likely the right one. Odd... I'll have to look into this further. I've never been able to reproduce it, unfortunately.

Marking this as game breaking.

Duplicate of #55.