Φόρουμ υποστήριξης - Firefox

I'm getting the XML Parsing Error message on Firefox after the latest update. I have tried every fix I can find in the help guide and the community section but none of them have worked. So far I have:

- completely uninstalled Firefox and everything related
- emptied cache of Chrome (which is what I am using to re-download Firefox)
- deleted everything in Windows Temp folder
- re-downloaded a brand new download of Firefox directly from the site
- run a full clean re-install of Firefox (same error message)
- restarted the computer (still getting XML Parsing error)
- unable to start Firefox in safe-mode as I don't have the button on the browser to do so.

Any other suggestions would be greatly appreciated as Firefox is my favourite browser and I want it back!