I'm using mogenerator 1.15 on Mac OS X 10.6.1. My model contains one abstract entity with two entities that inherit from it. The output has two problems:
I told mogenerator to put the underscore classes and the underscore-free classes in separate directories; all of the underscore classes, including the broken _Unit, are in the correct directory.
Can you post your model file? I can't reproduce this: http://dl.dropbox.com/u/14209/Repro_mogenerator_3.zip