See Garmin for an updated version of that Plugin. They created to add-on to Firefox, they need to keep it up-to-date as Mozilla releases new versions of Firefox.

Thanks, I will do that but it will probably take them forever, thought there may have been a simple solution

I contacted Garmin Australia and just got their reply as follows "Uninstall the Firefox 5.0.1, then go to the firefox website and download version 3". Now I am not going to do that, if I did, what happens as soon as I go back to firefox 5?