Server Error in '/Altiris/SetupPortal' Application

Hi, 

We have CMS 7.5 installed on Windows 2008 R2 Standard (64 bits). We obtain this error when we are going to open the console:

We have realized that Silverlight plug-in isn´t loaded on Internet Explorer (v.9), but the plug-in is available. We have tried to reinstall the plug-in and load console on another browser (Firefox), but it doesn´t work.

Also, if we click on top menu (ex.: Manage -> Policies), it shows a basic screen:

What can we do? Thanks.