This sounds like it's caused by a 3rd party repository. Where did you get mono and monodevelop from? What's the output of "apt-cache policy monodevelop mono-jit"?
** Changed in: monodevelop (Ubuntu) Status: Unconfirmed => Needs Info -- Monodevelop not starting after install https://launchpad.net/bugs/55344 -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs