I'm having the same problems, i have the the MacBook, 2.0GHz, 1GB, 80GB harddrive, superdrive and all that, and on monday limewire wouldn't stay open, i'd open it from the dock, then when thescreen to upgrade to limewire Pro came up, i clicked later, like i always do, and then it seemed to time out or something, it just shut down, so i turned the Macbook off, and back on and it worked, now as of yesterday it won't open, i've tried upgrading to V 4.13 beta, instead of V4.12 but i'm still having the problem