''locking this thread as duplicate, please continue at [https://support.mozilla.org/en-US/questions/1028741 /questions/1028741]'' Both Firefox and Zotero standalone crash immediately after opening. (I recently upgraded to Yosemite OS and upgraded to a new iMac desktop. However, the crashing did not immediately begin after OS upgrade and appears to be affecting the old computer as well.) I've tried the following: uninstalling Zotero and Firefox (including deleting Application Support files, including files in MS Word) and reinstalling. I've tried uninstalling one and only installing the other (e.g., uninstall Zotero and reinstall only Firefox, or the reverse), but nothing seems to work. When I open Firefox in under a different user account, it appears to work fine, which would seem to indicate the problem is hidden in some preferences file or other plugin that I don't know about. Help?