Norton release patch already for Firefox 6
maybe you are using Norton 2009 or 2010
Upgrade your Norton from previous version to latest version
* patch news are [http://community.norton.com/t5/Norton-Internet-Security-Norton/Update-Available-Firefox-6-0-Compatibility-Patch/td-p/512482 here]
* Norton Upgrade instruction are [http://community.norton.com/t5/Norton-Internet-Security-Norton/Norton-Internet-Security-2012-and-Norton-AntiVirus-2012-Have/td-p/526362 here]