COM interop object throws InvalidCastException in one project but not in other
I have a COM object I imported in my test C# solution.
Everything works fine and continues to do so.

Then I imported the same COM object in my actual solution and as a test implemented **the exact same lines** as in the test project.  
When I run the real project I get an InvalidCastException

<em>Unable to cast COM object of type 'CTWebReport.WebReportCOMClass' to interface type 'CTWebReport.IWebReportCOM'. This operation failed because the QueryInterface call on the COM component for the interface with IID '{5DFA18E8-4E71-4ADC-A812-6B166C242561}' failed due to the following error: No such interface supported (Exception from HRESULT: 0x80004002 (E_NOINTERFACE)).</em>

I searched my entire system for every reference to the interop and com library, this includes all the bin and obj folders I could find.
Except for the original COM library I deleted them all and for good measure cleaned out my recycle bin.  
No difference, exact same situation. Test project works, real project doesn't.

I don't know what to do next. Suggestions?
COM interop object throws InvalidCastException in one project but not in other
===

I have a COM object I imported in my test C# solution.
Everything works fine and continues to do so.

Then I imported the same COM object in my actual solution and as a test implemented **the exact same lines** as in the test project.  
When I run the real project I get an InvalidCastException

<em>Unable to cast COM object of type 'CTWebReport.WebReportCOMClass' to interface type 'CTWebReport.IWebReportCOM'. This operation failed because the QueryInterface call on the COM component for the interface with IID '{5DFA18E8-4E71-4ADC-A812-6B166C242561}' failed due to the following error: No such interface supported (Exception from HRESULT: 0x80004002 (E_NOINTERFACE)).</em>

I searched my entire system for every reference to the interop and com library, this includes all the bin and obj folders I could find.
Except for the original COM library I deleted them all and for good measure cleaned out my recycle bin.  
No difference, exact same situation. Test project works, real project doesn't.

I don't know what to do next. Suggestions?