If your browser reports that "moonlight" is "disabled" due to incompatibility, then here is what you need to do:

Make a backup copy of .mozilla (/home/your_user_name/.mozilla) before proceeding. This will preserve important bookmarks and other things you might want to consider later.

Now delete the .mozilla folder from /home/your_user_name/ and then reinstall all the addons and search plugins you had.

Now go to http://www.go-mono.com/moonlight and again install moonlight from there.

Note:

1) .mozilla is a hidden folder. Press (ctrl+h) to see it.

2) You can restore your bookmarks from backup of .mozilla

mozilla/firefox/om8xf96h.default/bookmarkbackups

This "om8xf96h" will look diffrent on your system. To restore open Bookmarks Window then use the "Restore" option from "Import and Backup" menu. Click on Restore and then navigate to backup directory and select the last modified .json file (like "bookmarks-2012-05-02.json")

4) To restore search engines (search plugins) copy the "searchplugins" folder from mozilla/firefox/om8xf96h.default/ and paste it to /home/your_user_name/.mozilla/firefox/om8xf96h.default