When you say 'Master' speaker, do you mean the one with the Red LED on it do you?
(Not just the first speaker connected to the MC200 directly)
In your surround system you may have your centre DSP speaker configured as a Master (red LED).
Now you move both floor-standing (slave) DSP speakers to direct connection to the MC200 you must set the one directly connected to the MC200 to be a Master (red LED) by re-typing it.
In any Meridian speaker setup there must be one (and only one) Master speaker.
There should be no reason at all that the G65 couldn't be repaired, it's still a current product from Meridian.
Rick