Ask Norton as it is not Firefox nor Mozilla that updates the Norton toolbar.

At first Norton only updated toolbar for 4.0 only and not 4.0.* and it then took them a long while to finally do a version bump to work on 4.0.* as they should have obviously done in first place.

Judging from how they handled it with Fx 4.0 and then 4.0.1 it may take a while.

http://community.norton.com/t5/Norton-Online-Family/bd-p/OnlineFamily

Actually apparently Norton did get their act together and released a patch for Firefox 5.0 release however it works best if Firefox 5.0 is installed first and not after the patch.

http://community.norton.com/t5/Norton-Internet-Security-Norton/Update-Available-Firefox-5-0-Compatibility-Release-for-Norton/td-p/478160

Despite claims in thread, the Firefox 5.0 was not actually released until June 21 as the sites were jumping the gun as early as June 17. http://community.norton.com/t5/Norton-Internet-Security-Norton/Norton-Toolbar-for-Firefox-5/td-p/475704