DONT use it Rated 1 out of 5 stars
i couldn't get into ff after installing this
i had to restore my pc . i hope nothing was hurt
More Info on Error
I just tested fresh installation and it works fine for me (FF 10.0.2). Can you tell me what operating system (windows xp, windows 7, mac etc.) were you using and what version of firefox you were trying to install this into (you can get firefox version by looking for "About Firefox" in the menu bar).
If possible could you also tell me what other addons you had installed in your firefox before you tried to install TabNavigator (please feel free to leave out this piece of info if you are not comfortable sharing it, I am just trying to take into account the possibility that the problem might have been because of some other addon).