I recently upgraded to the most recent Thunderbird version, then decided to install Lightening. Now this wierd stuff happens in TBird: - Nothing on Tools menu works except Message filters. Selecting other items yields nothing. - The Help menu has totally disappeared. Not even accessible by Alt-H. - Clicking a folder in the folder pane does not show messages in the right side. Messages only show if that folder's contents is launched into a tab. I've never used TBird like this, its terrible. - Tried restarting in safe mode. None of these aberrations is fixed, same behavior. Note: I never actually used Lightening after installing. Cannot verify that add-on install completed correctly. I've used Tbird without incident for years. This is terrible.