My SA keeps dissapearing too! I've got Firefox 18.104.22.168 and IE on a Window 2000 machine. My Firefox extension has to be re-installed every day! I leave my PC on 24/7, and after 24 hours, if I restart FF, my SA is GONE! Vanished! What's really wierd, is my wife has a nearly identical PC with Windows 2000 as well, and her SA STAYS IN FIREFOX! I think it may be an extension problem. Here's a list of my extensions:
Adblock Filterset.G Updater Adblock Plus Adblock Plus: Element Hiding Helper ColorZilla CookieSafe Cooliris Preview FlashGot FoxyTunes Free Download Manager plugin Greasemonkey IE Tab Minimize To Tray Enhancer Minimize To Tray MR Tech Local Install Reveal StumbleUpon
All of these are the latest versions. The SA plugin for Internet Explorer still works, but I never use IE!
I found the problem, after around 3 months. Long story short, i was using a FireFox extension called "Minimize to Tray Enhancer". It was conflicting with SA. I uninstalled it, Presto! It works again. There ya go.