Okay, that's a crash all right. Looking at your original specs I thought perhaps it was something else (I've seen posts where people called getting error message about not being able to play a sing because it had too many tracks a crash, which of course it wasn't), the 500Mc machine would have been underpowered for doing much in GB, but now I see you're using a G5.
Two things you can try: First, repair permissions. If that doesn't work, try logging in as a new User and see if it still crashes. If it doesn't, try deleting GB's .plist file