Hi,
The last lines of the log should be some kind of error like "Can't call method XXX" on line YYYY
Please try to catch that, the output you posted seems incomplete. If you run fop2 under gnu screen as mentioned it must show something like that before crashing.
I have fixed some of this issues in the next release, but I might need to squash some more of them, and the only way to find the problems is by user feedback, as usually crashes happen under certain conditions that are hard or impossible to replicate/reproduce (unconfigured buttons, extremely loaded servers, etc)
Best regards,