I had a problem with gnome-bluetooth's wizard, a couple of days ago, that I couldn't reproduce when running under gdb. Turns out that I'm too slow at typing or something, and the problem was a race (though a slow one).
There's a few tips and tricks in this class material. The one I was interested in was:
(gdb) break foobar_new
thread apply all bt
Then, every time you hit that break point, you'll get a backtrace, and the program will continue. I fixed that bug I saw :)