When your firefox freezes or crashes repeatedly, or behaves in an expected manner, it could be due to a buggy firefox extension. Mozilla has identified such problematic firefox extensions and created a list of how to fix them.
If you went through my 50 best firefox extensions, you will find fixes for several of them here like fasterfox, IE Tab, NoScript etc. Knowing about these bugs will help you identify the firefox extension that causes your firefox errors, fix them and uninstall them if required.
Found via Firefox Facts