I'm about ready to throw in towel and thought I'd try here for any advice.
I updated to FCP10.1 in December and been editing my project fine. On Wednesday this week I was editing and completed the project, (a 70min film) and fcp quit unexpectedly. I managed to reopen the project and rendered it. Now I'm trying to export it and it just closes bringing up error (final cut pro quit unexpectedly).
It's strange because I would of thought if the project was corrupt it wouldn't open at all but it does, I've trashed the rendered files thinking it was a bad render, I've rendered again without a problem but it does it same and just quits when I try to export.
You might need to do a clean install of Mavericks and FCPX. Some people have been having problems after updating.
I haven't had any problems with 10.1 sofar. I mean, in 2012, I had a 60 min experimental on my timeline, we started editing on 10.0.3 with an old-ass Firewire 800 drive. Other than the hard drive acting up, all worked well. And since 10.1 I've been flying.
"Always look on the bright side of life" - Monty Python