COM Exception

I have a scenario where a COM exception is thrown by the following vc++ code.
hr = alarmflag ? S_OK : Error(errormessage, IID_IErrSvc, E_FAIL);

in my project, this COM exception(thrown with a END and DEBUG button) is caught by a VB.dll and when we click the End button, the entire process crashes.(since VB.dll cant handle COM exception)

It is because, when we click the ENd button, a object is passed on to VB that it cant handle.

can anybody tell me whats the type of object that is passed when we click end button in COM exception.