I updated to 2011.5 a few days ago. I am experiencing similar crashing problems using my macbook pro. It has crashed 4x in the last 2 days. I've been rebuilding my "favorites" song list in preperation for a gig and periodically the program will crash as I am in the process of changing the number of "choruses" and then "freezing" the tracks. I get an error message from my OS x (10.6.8). Very frustrating, especially as I'm preparing for a gig tomorrow.