I sent an email to our Luminis manager describing the problem and asking him
to determine Luminis's XSLT processor.

In the meantime, I noticed something that may be important.  Luminis can only
take a stylesheet list file (.SSL) when performing an XSL transformation.  I
noticed that when I was adding the latest stylesheet to the channel, so I just
changed the extension from XSL to SSL.  Is that okay, or is there something
else that needs to be done to make it a valid SSL file?  If so, that would
explain why I'm getting such a cryptic error.

I'll write back as soon as I get some response from the Luminis manager.

Cheers,
Seth