AutoCAD .NET :: Ribbon Freezes With Custom WPF Objects?

I've been developing a way for our drafters to properly use a layer scheme. I implemented this by using a background database defined in Excel and loading this on startup. The interface is provided by custom ribbon elements as described in Fenton Webb's "UI Design featuring WPF" (autodesk university, 2009).

The ribbon contains the following custom elements:

- two series of radioboxes which are stripped of the default WPF multithreading

- a dropdown which monitors and manipulates LTSCALE

- a dropdown which selects values from the background database. 

- a UserControl which displays information from the background database about the current layer

All this has worked fine on multiple (about eight) computers with AutoCAD 2010 and 2012, vanilla and Map 3D. Now for two users, the workspace randomly freezes up. The freeze is just visually, commands are still executed and it is still possible to switch to a workspace without my ribbon in it, but my ribbon just stays on the foreground. This freeze happens when the user interacts with any part of the ribbon: switching tab, clicking buttons, etcetera.

The only way to resolve this problem so far is as following:

- Switch to another workspace without my custom ribbon tab

- Restart AutoCAD

- Switch back to the original workspace, everything works now

Directly restarting AutoCAD just results in another frozen interface.