Comment 4 for bug 574971

That's a possibility. In order to make sure it is not due to the language pack conflicting with any other extensions you have installed, would you mind testing this on a new profile that has just the language pack installed? You do not need to delete your default profile in order to do this. To create a new profile, launch the following command in a terminal:

firefox -ProfileManager

Then create a new profile, select it, and launch Firefox. Afterwards, you can install the Italian language pack on the new profile, then try replying to this comment to see if it crashes Firefox or not. Thanks in advance!