The forum software detected your Firefox as version 4, which seems unlikely. Could you check Help > About Firefox to get your current version information?

If you are using an extension to scramble your browser identification (user agent) that could explain the discrepancy. Otherwise, you may need to clear the preference that is misreporting your version number. See: How to reset the default user agent on Firefox.

it says version 4.0

can I just remove firefox? then reinstall? there is nothing I need to save

Just go to www.getfirefox.com, download the latest Firefox and install it over your old one.