Errors may look like this:
the message that is most important is “unable to load procedure in proc.dir" and can be caused by many factors.
One is a corrupt procedure directory. Another may be a name conflict with an existing procedure that is already in that directory.
The easiest way to work-around mcz installation issues caused by name conflicts or other error is to create a blank directory, set that as your default and let the MCZ file install into the empty directory. Find instructions for that method here:
Creating a new default directory
Follow the instructions here to rebuild a corrupt procedure directory:
Rebuilding a corrupt procedure directory