I'm getting this same problem. I've noticed that if I have a lot of media all playing at the same time, i.e. 2/3 video clips, sound clips all overlapping, then it will crash more regularly. This is extremely frustrating to work with. Anyone have any other solutions other than trashing preferences? Perhaps apple needs to release 10.0.8 asap?
I have been using FCPX 10.0.4 since it's launch without any problems until this afternoon.
For some reason when I try to load the library the program crashes.
Clicked reopen, shut down without a resolution. (this happens both with and without the external Thunderbolt drive)
Currently updating to 10.0.7 hoping to get a "fix'
Memory 8 GB
Mac OS X Lion 10.7.5
Thunderbolt 1 TB