I had some mp3s cause iTunes to crash, it's more than likely a problem within the library and a faulty mp3. Remove that mp3 from the library while you can, because I had one that wouldn't delete, anytime i tried to do anything to it, iTunes would crash. I converted the mp3 to ACC and it was fine. I had to reimport all my music and i lost 2 years of music tracking because of this. I had a thread about this when 4.5 came out.