Yep, that’s the reason. As I said in my earlier post (and in the dev program page), if you’re creating an expansion pack (and that’s exactly what you’re doing), you should specify two parameters. The first one will tell the name of the base pack, and the second one will be the pack you’re working on.

So it should be: ePicPackageGenerator.exe char_mama char_mama_BPGbigguy