Ah, I see the g3 option generates extra debugging info. I'll give it a shot. I have a bug open with Apple about this anyway. It has proven to be very hard to pin down. Restarting Xcode will usually eliminate the problem and let you step through code... ONCE. If you want to do it again, you have to quit Xcode, reload the project, and go. Infuriating.
And often it will afflict some files but not others. I checked the currently troublesome one to make sure it was -O0.
