Input Focus Problem for Shell Application

I'm using Windows Embedded Standard (not 7) and have successfully implemented
Sean Liming's "Different Shells for Different Users" (with a lot of help from
our FAE at Arrow) but I'm having a problem where my shell application
(written in C# .NET) doesn't get keyboard input focus. I have to click on it
to give it keyboard focus but in deployment this system won't have a mouse
attached to it normally.

The lack of imput focus is persistent (i.e. it doesn't time out and get
focus). I put a this.Focus() in my Form1_Load() method but that doesn't
help. When the application is launched normally it receives keyboard focus
and behaves as expected.

Any help is, of course, greatly appreciated,
Jeff Cooper