I have a very large solution to which I am trying to add the ultraTree (v9.1) to an existing form to replace the windows treeview control.

As soon as I drag the ultraTree component from the toolbox I get the following error:

After I close this I get a bunch of "Object reference not set to an instance of an object" messages, even though the designer failed to load the control onto the form.

This happens when I add it to a new or existing form in this project.  It does not happen If I drop the control onto a new form in a new project.  Any idea what might be conflicting with this? 

The application previously used v2.0 components and was upgraded to v9.1 without much incident, however all references to v2.0 components have been removed.

The solution is too massive to rebuild, so hopefully you might have some insight into where I might begin to look to find the conflict.