Firefox, Norton Confidential and Phishing protection

I'm running OS X 10.6.8. and have Symantec v 5.1.2 (22) and Firefox 15.0 on my Mac, all the latest up-to-date versions. Everytime I open Firefox, I get the following message - This version of Firefox is not supported by Norton Confidential. You will not be protected while browsing the Web. Norton Confidential cannot protect you while you use this version of Firefox. Phishing Protection requires Firefox 1.5 or later.  There are no issues with Chrome, Safari or Opera!

 

This has only happened since updating Firefox today. Any ideas to help would be appreciated.  If responses include using Terminal, I've not used it before!