I've recently had a few problems with the Wikalong extension for Firefox. It seems to have issues with a couple of other extensions, in particular DuplicateTab and UndoCloseTab. Instead of letting those extensions do their funky groove thing and create a duplicate tab, or regenerate a previously closed tab, the newly-created tabs are blank.
Not sure if the issue is with Wikalong or DuplicateTab or UndoCloseTab. But I found disabling Wikalong fixed the issues (and the tab extensions are more important to me at the moment!).
 Which is a terrific idea incidently! Kudos to the author.