Have you looked at the error log? If not, then try it. It will tell you exactly where the error occurred and it may be crashing because of some app having been installed that does not like your OS. Unlike the Windows error log, the OS X error log can be pretty informative and help you resolve your problem.
Did you upgrade to Snow Leopard? If so, did these errors begin after the upgrade? If so, then you need to go to Library -> Preferences and delete the Cinema 4d plist files. Again if SL, you may also need to visit Cinema site and download the SL compatible version if they have one.