Hi SilentStorm
Would you be able to attach the fcpxml in question please, would you be able to clear the console on your machine and attempt to re-import and copy the contents of the console for us please. I ask as the error message does not really give us a lot to go on, so it could either be something fundamentally odd with the FCPXML or something system related (hence the console). Another useful thing to do to check the FCPXML is to see if you can re-import this back into FCPX, and what happens when you try.
Yours Sincerely
James.