Smart Client Security Issue

I developed a simple windows VB.Net app. It's a smart client that loads an
assembly from a web server.
The client machine and the server machine are both in a local network. When
the client tries to load the assembly from the server, I get the following
error:

System.Security: SecurityException: Request for the permission type
System.Net.WebPermission, Version=1.0.5000.0,..., failed

I run the Trust Assembly under .Net Wizards and configured my assembly to
Full Trust. I still get the same error.

How should I configure the security of my virtual directory in IIS?

Thanks for any ideas.

Cesar