Ok, learning something new everyday mate.

Google Earth plugin for this has some bugs with certain Firefox series.

Supported browsers currently include Firefox 2.x, IE6, and IE7, all only on Windows.

http://earth.google.com/plugin/

Above is the latest version of Google Earth Plugin. See if you have the latest version there. If you do then I assume that you are not using Firefox 2.x.

I'm not even sure if Firefox 2.x is the latest edition or an earlier one????

Thats the only issue with new browsers these days...Life was ten times easier in the 90's...lol