I am able to view the 3D content fine in IE7. I am not seeing it in Firefox. Please tell me what version of MTS3Interface.js you are using. You can find it by opening your MTS3Interface.js file in a text editor. The version number is at the top.
upon further investigation it does appear you are using an older version of MTS3Interface.js (3,3,0,29). Please download the latest version (5.0.2.29) from our developer central site (http://developer.viewpoint.com). It is in the blue box in the middle of the page. It includes instructions for using it properly.
This would be a good reason why it is not working in Firefox. The old MTS3Interface you are using does not support firefox.