Some time ago, I installed a Firefox add-on that allows Ctrl-Tab to jump between tabs more intelligently. It remembers the most recent tabs and switches back and forth in that order. It will even display a list of previews (much like Windows Alt-Tab) of the tabs. This was back in the FF3.6 days or so.
When Firefox 4 came out, the add-on disappeared from my list of add-ons, possibly due to some conflict. However, the functionality is still there. It works exactly as it did before.
The problem is that I have strong suspicions that this add-on leaks memory like a sieve. My other computer with Firefox uses much less memory, while the computer with the phantom add-on can get to 1GB+ of memory usage if it isn't regularly restarted.
How do I remove an add-on that is not in the add-on list? And how can I do this safely? I don't want to break my FF install, nor do I want to have to reinstall everything.