You may need to run LiveUpdate and reboot a few times before your product is completely updated to the latest version. It will appear in the LiveUpdate history as Norton Toolbar Add-on for Firefox.
If you are running Firefox 18 and Norton Internet Security or Norton 360 126.96.36.199, and still do not see the Norton Toolbar, please check and ensure the Norton Toolbar plugin is enabled. You can do this by clicking on the Firefox menu, selecting Add-ons, and then clicking Enable next to Norton Toolbar.
Also said it can work best if you do Norton update first and then install the new major Firefox release.