Custom controls from dll not showing up in toolbox

See more:

VB

I am using VS2010 (Vb.Net) with .Net framework 4.0.
I have made a classlibrary project with a number of custom controls. When I put the source of this custom control project in a solution with another project I get all these cutom controls in the toolbox rightaway.

However when I make a dll of this classlibrary custom control project and put it in the solution, I don't see these custom controls in the toolbox. Ofcourse I referenced the dll and compiled the project.

In the "tools\options\windows form designer" settings I also made sure that AutoToolboxPopulate property is set to True.
In the custom control class itself I have added the setting <toolboxitem(true)>, however this is said to be the default.

Furthermore I know you can manually add toolbox items by right clicking on the toolbox and through "choose items" browse to the dll and add them. However then they are also not neatly categorized, but added with the common controls.
But this is not the way I want to do it. I want the custom controls from the dll to show up the same way as when I add the classlibrary source code of the custom control project to the solution.
In my opinion it should be enough to reference the dll. How else could you make a programmer-friendly distributable class library ?

Does anyone know why this doesn't work with the dll ? Am I missing something here ?
Thanks in advance.

Wietze