Dynamic User Control ( Type not defined issue )

Hi, I went through the whole forum looking for a solution for my problem, but to no avail, so I'll give it a try posting and hope someone can help me figure out what my problem is.

 I have a web user control called "details.ascx". Right now it's pretty empty. I use it in a ajax ModalPopup to display details about a transaction.

I have no problems dynamically loading a "normal" user control with loadControl or addressing it. But in this case, I want to load a "custom control" (if that's the word for what I'm doing).

But I keep getting the "Type not defined error". In the example I provided, all I wanted to do to test if it works is to setup a label text in my custom control

Here's the important code :

---DETAILS.ASCX----------------

<%@ Control ...