I cannot get Mac the Ripper to work on any computer I try (I've tried it on 3 different computers...1 desktop, 1 powerbook G4, 1 macbook). I try to adjust settings. It shuts down. I try to select different preferences. It shuts down. Is anyone else reporting these problems?
Sounds like you may have a corrupted download. I would try downloading again. Trash the old file first. Also if you are using a beta version you should try to roll back to 2.66.