My xenserver was freezing at the splash screen on bootup, so I used the "fallback" parameter during boot.
Now it brings me to xenconsole with the error at the bottom:
"The server failed to handle your request, due to an internal error. The given message may give details useful for debugging the problem.
Message: object with type VM and id xxxxxxx/config does not exist in xenopsd.
the xxxxx is a very long string that looks like an UUID.
I am still able to connect via xencenter.