We are attempting to move a large development project into the .NET
age over time.  We have a large number of ATL-based COM objects in
this project.  Following the "Journal Poster" example provided by MS,
I have converted some of my COM projects into mixed code so that there
is both a .NET and COM interface to the underlying logic.  So far, so
good.

In one of these former COM projects, four additional COM objects are
within from the underlying logic as a matter of executing the main
interface method.  Our testing shows that this all works perfectly
well through older programs that are using this project as a COM
object, but when accessed as a .NET class library, only three of the
four objects are loaded properly - attempting to create the dispatch
for the fourth COM object causes a COM exception reporting that the
object is not registered.  

I have traced the problem right down to the call to CoCreateInstance
and I have checked the registry, but I'm at a loss as to how to
proceed from here.  Any ideas?  Other than not being registered, what
can cause a "not registered" message?