Silverlight 4 xap doesn't show up in Firefox, but works in IE

I recently upgraded a Silverlight 3 开发者_如何转开发web project to Silverlight 4. All i had to do was rebuild the code in VS 2010 with toolkit et al installed and host it on server.

On testing, the SL xap showed up in IE 7 and worked as expected. But, on Firefox, the xap is getting downloaded but doesn't showup. Little bit of firebugging shows that, the xap is downloaded successfully to browser. Right clicking the page confirms that SL runtime is not loaded. Inorder to confirm that i had SL4 runtime, i visited Silverlight.net site and tested some of the showcase apps, which show up fine.

What should i be looking for, if the XAP is getting downloaded successfully, but not loading the runtime? Appreciate any suggestions or questions. Many thanks!!

The div hosting siverlight might not be showing, or the correct size in ff.