Hey, between the link you gave me and some snooping around at microsoft, I think I was able to figure it out...

It appears the 2.0 release of the .Net redistributable does not contain the mshtml interop assembly, and so I had to install the SDK (which does contain it) on the operator machines to get everything working smoothly.

MS says,
"All post-Beta 2 releases of the .NET Framework SDK now include a primary interop assembly for Mshtml.dll. However, any organization that distributes the .NET Framework through the .NET Framework Redistributable must not depend on the existence of this interop assembly on clients. "

http://support.microsoft.com/?kbid=311295

It's a bit of a roundabout way of doing things, but it works :-)
~ Dana