You can try this extension if you have compatibility issues with other extensions after upgrading Firefox:

• https://addons.mozilla.org/en-US/firefox/addon/add-on-compatibility-reporter/

If you still want to downgrade, see here:

• http://releases.mozilla.org/pub/mozilla.org/firefox/releases/latest-4.0/win32/en-US/
• installing firefox

I have the same Roboform problem. I tried the link to go back to version 4 of Firefox and the link does not work. Site Not Found error!

My worked ok but I did it a different way. Fortunately I had the original download still on my pc so I just ran that again. Roboform works ok now except that I can't get out on upgrading to V7 and having to pay extra. Earlier I had tried just restoring to an earlier date but Firefox (presuambly V4) just came up with a virtually blank screen.