mozilla firefox перестал работать fast dial

Попробуйте установить бета версию 3.5b1 с сайта разработчика https://addons.mozilla.org/en-US/firefox/addon/fast-dial-5721/versions/
Про нее написано
A new Beta Version of Fast Dial is uploaded as 3.5 (in the development section)
Should work with Firefox 4, Firefox 5, and Firefox 6.
We are waiting for your feedback before releasing it officially.
please use http://userlogos.org/node/14288 to log problems.
Features:
- Press Ctrl+T to open Fast Dial page.
- Set browser home page to "about:blank" to have Fast Dial opened on startup.
- Add new sites to Fast Dial by right-clicking site page and choosing "Add to Fast Dial" from the context menu.
- Open thumbnail Properties from context menu or by moving mouse cursor over the top-right thumbnail corner.
- Assign a logo to any site on Advanced page in Properties dialog. Get more logos at userlogos.org site.
- Use drag-n-drop to change thumbnail position. Ctrl+drag to move thumbnail into a folder.
- Scroll Fast Dial page by mouse wheel or PgUp/PgDown keys if there're more bookmarks that fit on the page.
- Enable thumbnail preview in thumbnail Properties dialog. Then left-click and hold on a thumbnail to see the preview.
- Customize any aspect of Fast Dial in Preferences.
- Themes. Use predefined ones, get more at userlogos.org or create your own.
- Set any bookmark folder to be Fast Dial home.
- Export/import any bookmark folder.
Так что должна работать с Файрфоксом 5 и 6.
Выставите, как написано, стартовую страницу Файрфокса в настройках "about:blank" и пробуйте.

в дополнениях он отключен как несовместимый?

C 57 версии снова несовместим. Firefox меняет подход к addons, теперь всё должно существовать в виде WebExtensions.

https://addons.mozilla.org/ru/firefox/addon/fast-dial/
https://blog.mozilla.org/addons/2016/11/23/add-ons-in-2017/