According to RPG gamer:
This was the case with Enix's recently released Star Ocean 3: Till the End of Time, which featured its own lock-up bug appearing during battles. Enix has remedied that problem by distributing a new bug-free version of Star Ocean 3 and offering free replacement disks for the unlucky recipients of the previous version.
It could be that you've burnt a version of the game that had the lock-up bug, which seems to be the case as it happens during battles. I guess your best bet would be to search for a version of the game that is confirmed to be bug-free.
