As you know, Firefox 3.6 was released on January 21st 2010. We plan to support Firefox 3.6 shortly. We're working on compatibility, and should have this resolved soon.
If you have Norton Internet Security 2010 you can update to 17.5 through LiveUpdate. The Norton Toolbar included in 17.5 is compatible with Firefox 3.6. We plan to have IPS compatibility available shortly.
Norton 2009 customers should update to Norton 2010 (free of charge for active subscriptions) using the Norton Update Center.
Please know we're working as quickly as possible to test and finalize our compatibility and support for the newly released browser.
Check back here for updates as they become available.
Thank you for your patience!