My guess would be that the assembly is failing to load due to a missing
dependency.

I should point out though, that using RegPkg.exe to register your package
in a deployment/install scenario is not the proper thing to do. It's my
understanding that the RegPkg.exe utility is not redistributable, and you
should avoid self-registration in your retail setup.

RegPkg.exe is very useful for development and test environments, but you
should be relying on the Windows Installer technology to add the necessary
registry keys. RegPkg.exe has a couple of command line switches that will
produce a .REG or .VRG file which can be useful in identifying the keys
you'll need to add, but I would not recommend using it as a way to register
your package outside of a development or test environment.

Sincerely,
Ed Dore [MSFT]

This post is 'AS IS' with no warranties, and confers no rights.