Acess methods of OCX in C# code-behind

Hello,
I have an OCX that works fine on the client side.  However, I need to access the control's methods in the C# code-behind. 
I added a reference to the OCX and am able to create an instance of the class and see its properties and methods.  However, when I run the application I get an error on the line where I am trying to access the control's method.  The error I get is:
{"Catastrophic failure (Exception from HRESULT: 0x8000FFFF (E_UNEXPECTED))"}
System.Exception {System.Runtime.InteropServices.COMException}


Any ideas?
Thanks!
Mark

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