This issue is also related to http://forums.adobe.com/thread/1236588?start=40&tstart=0. On windows we get this error if flashfirebug plugin to firefox is installed.
We are investigating the issue further for a fix. However, for the time being uninstalling the flashfirebug plugin should fix the crash. If you prefer editing the configuration files manually, then alternatively you can just comment out or remove the PreLoadSwf key in mm.cfg (found in your home folder) to avoid the crash.
- Dharmendra.