Did it all work with the 5.1DDD type the first time?

As George said above when you went back to type the second time you would have reset all your changes when you loaded the config.

Just one last thought did you set the product version to "2.50 or higher".

Main system; 861v8 ID41, DSP8000SEU fronts with DSP5500 centre and DSP7000 rears (all in lovely silver) 504, HD621
Second system 861v4 ID40 LPS, G98DH, 504, HD621, 2x DSP5200 with DSP5200 centre
MD600 tucked away in study. Lots of other Meridian!