It's somewhat hard to tell what your actual application is doing, but it sounds like you may be instantiating the COM object and then attempting to access it from another thread, perhaps in a Timer.Elapsed event. If your application is multithreaded, you need to instantiate the COM object within each thread you will be using it in.
A good way to debug this issue is to do the following:
1.Write a class that inherits from the Interop class (otherwise known as the runtime callable wrapper or RCW).
4.Call your new class instead of calling the interop class directly
5.Add breakpoint to DetachEventSink and Dispose
6.See who is calling these methods out of order
Editor, DotNetSpider MVM
Microsoft MVP 2014 [ASP.NET/IIS]