COMException : Creating an instance of the COM component with CLSID {…}

I recently changed my NAnt build script, as part of its post-build cleanup step,  to unregister all .NET COM interop components after doing the build. Now my unit tests fails with this error:

System.Runtime.InteropServices.COMException : Creating an instance of the COM component with CLSID {596C3AA2-D5EC-4F86-85E3-7FAF86EC17A3} from the IClassFactory failed due to the following error: 800a005b.

What’s the cause?

Here are the facts: My .NET lib X depends on a  COM lib Y (596C3AA2-D5EC-4F86-85E3-7FAF86EC17A3), which depends on COM lib Z, which in turn invokes  .NET COM interop lib N.

It turns out that the real culprit was N, which wasn’t registered for some reason, even though I’ve told it to register via the regasm NAnt task.

Well, as it turned out, I needed to add the codebase=”true” attribute to the regasm task that registers N, which makes sense in hindsight, because my DLLs are not all in the same directory. Another “doh!” I suppose.