In addition to the procedure I mentioned in the previous post for uninstalling Firefox 3.6 and reinstalling the previous version, you should also uninstall and reinstall Java.
From the Windows Control Panel and Add Remove Programs (or Programs and Features) find Java __ Update ___. Remove or uninstall it.
Then open your browser, either Firefox or Internet Explorer, and go to http://www.java.com. Click the button that says FREE DOWNLOAD and follow the steps accordingly. You can un-check the check box during the installation process when it asks if you want the Bing / Google / Yahoo toolbar. You don’t need it.
IMPORTANT: You only should consider going through these procedures if you are really having problem with the new version of Firefox — 3.6. Feel free to contact me for personalized advice.