New Post: MEF Second Time Load Module

Hello,
I have an issue using Prism and Mef in silverlight , I have a module which contains one view.
So when I click on a button in the shell page , I navigate to a view that defines a region which load the module in code behind.

For the first time all works fine, and the module was downloaded correctly in the client side, when I try to access to it for the second time an exception is generated ,
So I want to know how to activate a module which I has already downloaded it

Thanks,