Hello Anders.
Sorry for the tardy reply.
I created all of the MSIs via Regform.exe, not directly in VS.NET. Also, I'm certain that I'm using the correct version of Regform -- the one that deals with 2.0 managed code, not 1.1. At this point, I've tested the MSIs on a couple of machines and am getting mixed results. It all works on one machine that has .NET 1.1 and 2.0, Infopath SP2, etc. installed. Another machine with the same setup won't let it work.
Is it possible that Infopath is configured to "prefer" one .NET installation over another? That is, if it's configured to use 1.1 managed code, then I would get errors when it tried calling 2.0 code, right? But I'm not certain that that's how Infopath interacts with .NET managed code. At this point, I might try uninstalling Office and .NET 2.0, then reinstall. I would rather not have to do that, especially on my clients' machines. Do you have suggestions for what I might try?
Take care and thanks for your help! I'll make sure to post if I find a work-around.