Symantec have released updates for Norton 360 and Norton Internet Security to make them compatible with Firefox 4, for details see http://community.norton.com/t5/Norton-Internet-Security-Norton/Firefox-4-compatibility-hotfix-is-now-available/td-p/428894

TonyE,,, thank you so much for your help, your answer and link solved the problem,,, no sweat...

Thanks very much, Tony! worked like a charm. But I wonder why Norton didn't say a word to me about this or even notify me that a Norton update was available....!!

Well, it also worked for me after I'd first installed Firefox 4. However, today, after installing 'an important update', the update disabled the Norton toolbar and safe site indicator and now the Norton fix does not work, and won't even reinstall.

So, once again, what now, please?

Frankly, while being an admirer of Mozilla, I think it disgraceful that Mozilla does not enable one of the best internet protection software tool bars to work with its latest Firefox version!

Norton "screwed the pooch" when they updated their Firefox extensions for Firefox 4.0 - they didn't code the maxVersion for those extensions properly so that Firefox would not disable them after a minor version security update. Now Norton says they'll have a fix available in two weeks for 4.0.1.

IMO, you live with Norton's fock-ups and wait for them to fix them, or you decide which is a more valuable program to you - Firefox or Norton - and get rid of whichever is less valuable to you.

Exactly the same thing that happened to me - shortlived relief! And after I updated Norton, I suddenly started getting a notice that I had used all my online storage. I had plenty the day before I updated, and not enough the day after! Not only that, the updated Norton no longer has the "purge file" option at the online storage site and so I can't figure out how to delete anything. Grrrr. Vicious technological nightmare cycle.