Glad to hear you worked it out, good luck! Looking around there are a few levels of cache around whether addons are enabled, I guess those are what you need to clear it.
It's a temporary hack, but you might also want to look at temporarily loading extensions with about:debugging, this works even in official release.
Edit:
For anyone else trying to auto-obtain the latest stable Firefox nightly, here's a hacky command (change for your OS as needed):