The most likely cause of crashes on Mac OS X is a plugin conflict. Please ensure that there are no outdated webcam drivers installed on your computer, and try disabling camera plugins such as iGlasses.
The old DIVX and 3vix video plugins can also cause this issue. To remove them, browse to the Library folder on your Macintosh HD and go into the QuickTime folder. Drag any files with ‘divx’ or ‘3vix’ in the name to the trash, then try relaunching the software.