DLL / Typelib / COM

I have a C++ DLL which holds COM code. When trying to access the interface with VBA code, I am getting these error messages:

atlTraceCOM - ERROR : Unable to load Typelibrary. (HRESULT = 0x8002801d)
atlTraceCOM -   Verify TypelibID and major version specified with
atlTraceCOM -   IDispatchImpl, CStockPropImpl, IProvideClassInfoImpl or IProvideCLassInfo2Impl

I checked everthing - esp. version numbers - with OLEVIEW and the registry editor and cannot find something wrong. The COM is also working perfectly from another C++ client application (where I imported the .TLB first), but I cannot access from VBA ?!?

Any ideas?