Rated 3 out of 5 stars
same for me: when I use this add-on, on restarting FF, I find it has 'removed' itself from the add-on bar and the preferences box is unavailable. I have to reinstall it for it to be accessible again. FF 17.0
I tested it again, I let the add-on perform a auto restart of the system and after that, I can not access the options of Auto Shutdown. I first have to install the add-on again to get access to the options and to see the shutdown button.
Windows7 x64 SP1 Firefox 17.00
I can't reproduce this bug, so I can't fix it.