Objects in GAC are not available to VS 2003

have a strange behavior in VS 2003IDE. Some of the components/objects
(provided with different MS) as well as some I developed does not appear in
the list of .Net components when I click on "Add reference" to a project.

To double check, Icreated a new C# class library, signed it with a key
generated with SN utility, added it to the GAC using
gacutil -k myclass
When I browse the GAC list in admin>.Net framework I can see my component as
well as plenty of others which I don't see in VS IDE.
Thanks for your help