Trying version 1.7 at least narrows the field for me. Was going to ask you to check the version of the ML Bevel Reflect app or Exe file in the plug-ins folder to see if it is version 2. Also I wondered which version of the portable gimp you were using?
Oh, Skinnyhouse! I feel silly about this but the reason for the above errors for me was that I thought I had all the needed files active. However, when I was checking again, I realized that the BRL 1.7 was not activated in the Addon Manager. Now it is working perfectly!