Are you trying to use an ActiveX (OCX) control in a .NET application?
Did you add the reference, create a class and are quite happy at how easy it was?
So, now you try and run the application and CRASH - Catastrophic failure!!!
The problem is that an ActiveX control requires special handling when embedded into a .NET application. The easiest way to do this is:
1. When in the Form Designer, open the Toolbox window and right click one of the tabs.
2. Click "Choose Items..." menu option
3. Select the "COM Components" tab
4. Find your control in the list and add it.
5. Drag the control to your form.
This will create various new Interop classes, including special event handlers for your events, et cetera. It should work now.