It has got to be something with the site. Cause i get the same issue. Loads up fine with IE8 no less. But wont load with Firefox or Opera at all. I know my WMP is up to date and i have all the WMP plugins installed.
The stie must not be coded to rexognize Firefox or any other browser but IE. Could probably use the User Agent Switcher extension to make it work. But the stie is just not made to work with Firefox.