bacchanalion/joakim,
In another thread (General Mac OS X support, or something like that) it was suggested that you disable the ultrapeer option to stop the "quitting unexpectedly" problem. It's been working for me this evening after experiencing a crash every two minutes, and has been working for 2 weeks for the person who posted the problem. (preferences>((opens a box call "options"))>speed>check disable ultrapeer.)