Tools > Addons > Extensions - does that Norton extension appear in that listing?

"... They also point to the fact that I can access the toolbar through IE 8 as proof that their product is not at fault. "
That answer from Norton wasn't accurate. IE uses a different version of the Norton toolbar than Firefox needs.

^I wonder if the person who said that has even used Firefox.

It makes sense that Norton may use a different toolbar for Firefox. However is the toolbar extension a Norton product or a Mozilla product? Given the full re-install I keep wondering if there is a setting in Firefox that needs to be changed...

^ You know how "support" works, they read from a prepared script, and if it isn't covered by the script, they "wing it".

OK. But where do I go to find a solution?

I have solved the problem by uninstalling the DVDSoft Toolbar. This by the way was not easy. Uninstalling the toolbar using the control panel removed it from the program list but not the computer and it still showed up in Firefox (nasty little bugger). I was able to remove it by removing all programs from DVDSoft.

The Norton toolbar for Firefox is made by and supported by Norton.

Mozilla has had very few Extensions over the years where they made or were involved with themselves and some of those would even be considered third-party as the Mozilla worker was supporting it independently themselves.