>From Notes Help:
>COM interface is available on a computer containing any of the following:
>
>Domino Designer Release 5.0.2b or later
>Domino Server Release 5.0.2b or later
>Notes Client Release 5.0.2b or later
>
>The Domino or Notes software must be installed but need not be running.
>Installation of the Domino or Notes software makes a type library available and registers the following classes:
>
>Lotus.NotesSession
>Lotus.NotesSession.1
>
>You should have the class registered on your machine. If you don't, I suggest you reinstall the client and see if that takes care of it.

Reinstalling didn't help.