New clue Rated 5 out of 5 stars

Hi, I have just got new findings: after testing with different profiles, I found that there is no problem with other add-ons. If a profile is in a session with only 1 window, then next time when Firefox starts with it, the menu is normal. And if a profile is in a session with multiple windows, then next time Firefox starts, the session and the windows are restored, and the Persona Switcher menu items only appear in the window which opens last, but in other windows the menu is empty. Hope this helps.

This review is for a previous version of the add-on (1.8).  This user has 4 previous reviews of this add-on.

It helps a lot! I'll work on hunting this problem down. Thanks!

Can you try the 1.9 version? I think it fixes this problem. It hasn't been approved yet, but it at https://addons.mozilla.org/en-US/firefox/addon/lightweight-theme-switcher/versions/ Thanks much!