I recently updated my 3.0.12 to 3.5. My 3.0.12 had add-ons (stumble, digg, and FTP client). When I updated to 3.5 these add-ons were not compatible so I changed back to 3.0.12. However, now that I've changed back, the add-ons will not initiate. I can see them in the tools section and they show as enabled but they won't launch. I found that my old 3.0.12 is launching in safe-mode which could be keeping the add-ons from showing. I've done everything I know how to get it out of safe mode and nothing seems to work (file exit, re-installing, etc..). Can anyone help?
Uninstall Firefox from uninstall, then find the firefox directory and delete it. And download a fresh firefox install and install it.
What he said to do is called a clean install, it's a good way to solve problems with many different programs.
For a clean install, uninstall any previous versions, run ccleaner to clean up the registry, defrag the installation drive, finally, re-install the program.