Strange form of "Class not registered"

I've read through the messages here about "Class not registered" since
June 1999, but don't see anything similar to the case I have.

I'm trying to use an ActiveX component (VpxListPlayer.ocx) that comes
with the SDK for the Optibase VPXpress MPEG decoder board. I've
imported the component and created a package that contains it, and I
see the component on my Delphi 5 component palette. When I try to add
it to a form, I get the error message "Class not registered". This
error message contains no other text, such as an identifier of the
missing class or DLL. I don't know whether or not it normally has that
information, though I would hope so.

Optibase SDK tech support says that this component is automatically
registered during installation of their SDK, and indeed one of their
sample applications, which uses it, runs correctly on my development
computer. That would seem to indicate that the ActiveX component is
correctly registered, along with anything else it requires. However,
I've run REGSVR32 on the OCX, and it reported successful registration.
I've also run REGSVR32 on every DLL in their SDK, just in case, but I
always get the message: "x.dll was loaded, but the DllRegisterServer
entry point was not found." I assume this means that the DLLs are
manually loaded, and not loaded via registered class IDs.

Naturally, I've tried uninstalling and reinstalling the SDK, removing,
deleting and recreating the Delphi package containing the component,
etc., without success.

By contrast, I've installed the ActiveX component on my laptop (which
does not have their decoder board on it, naturally), and encountered
no problems. I'm able to drop the component on a D5 form their without
difficulty. I don't really think the problem has anything to do with
presence or absence of the board. I assume there's something different
about the procedure I've used, or the software environment, on the two
computers, though I can't detect any differences that I think would
cause this.

Can anyone suggest what I might be doing wrong, or how to debug this