(I apologize for the formatting above... I'm adding line breaks to make this comment easier to read).
Tested it just now. It gets to the installer screen, and begins unpacking files after I click Install. But as soon as that's finished, it says it failed to install.
This may be relevant (or not)... in the temp folder, under the GUID path, it extracts 16 32MB cab files, a setup EXE that I created to install my program,
and the SupportFiles directory structure into a folder literally named #CABPATH. As soon as that is done, the error message pops up and the *.cab files
are deleted (but the #CABPATH and setup EXE are not).
Here's another strange thing... the installer was ~250MB before, but is now around ~491MB. Looks like the folder is being embedded twice now.
Thanks for your help!