Even if it doesn't officially support Firefox 9 now, you can make it work by disabling the addon compatibility check. To disable the addon compatibility check you can install Add-on compatibility reporter ( https://addons.mozilla.org/en-US/firefo ... -reporter/
) and disable the add-on compatibility check or;
1. Write about:config on your address bar and press enter
2. Accept that there are dragons in there
3. Right click on that page
4. New > Boolean
5. Write "extensions.checkCompatibility.9.0a"
6. Set it to false
7. Restart your browser
After these steps the addon will work flawlessly. I'm currently using SP on a Firefox Nightly Build.