Hi
Can you access the follwing file?
http://myserver:3689/Silverplay/ClientBin/SilverPlay.xap
That’s the actual Silverlight Package which the html page should be able to download.
Running Firefox 3.0.1 myself so that bit should be ok.
If you want I can try to debug it from my location. But for that you would have to provide me with your hostname. You could write me a private message with that info.