I deployed the Sitefinity site from local to DEV and STAGING servers and the document uploader works on DEV but suddendly disappear on the STAGING server.

Correct Screen
correct screen

Error Screen
blank document upload

I’ve created a forum post but received no good answers. The dude kept asking me to install Silverlight Tools on all the machines. I don’t understand why we have to install silverlight on all machines and which silverlight exactly to install as there’re browser plugin, silverlight tools, silverlight framwork etc. And I cannot install silverlight tools unless the prerequisites, Visual Studio 2010 and Web Developer Express 2010, been installed which I absolutely don’t want to do. Also on the DEV server, there’s not a single instance of Silverlight installation was there and the uploader’s working just fine so I really had a hard time figuring out the issue with STAGING site. The forum responds were so slow, so I created a ticket and the same dude replied as followed:

Can you enable Firebug and check what errors come up in the Net tab when you try to access the Upload section? Also is there a way to provide RDC to your server so I can inspect the settings in more depth?

Ofcos I don’t want to give RDC access but I checked the Firebug and that really helps figure out the problem.
With the help of Firebug, I got 404 file not found for Telerik.Sitefinity.Silverlight.xap file with the error below:

Unhandled Error in Silverlight Application
Code: 2104
Category: InitializeError
Message: 2104 An error has occurred.

Now that’s some good hint, so I checked the path and the file exists on the server so must be the file permission issue; I googled the error message and found out that it’s all to do with missing MIME Types on STAGING server.

mime types

I’ve added these 3 types to the server MIME types list and it fixes the problem.

.xap application/x-silverlight-app
.xaml application/xaml+xml
.xbap application/x-ms-xbap
Ref: Configuration IIS for Silverlight Applications

I wasn’t happy with the support but thank god he at least gave me a hint to check with Firebug.