Thanks for your help, unfortunately I've tried all three installers, opening without extensions, and all the other suggestions I'd already tried. So far none of those has had any effect on it. I think I may upgrade to OSX here shortly, though... Still, I'd like to find out what the problem is. It seems to me I've had it once before with another Java program and I fixed it somehow, but I can't remember! Frustrating! (Maybe I reinstalled MRJ... but that didn't do anything this time.)