I have done that a number of times. I do think it is something with the ID41 card or a comination with another card in the 861. I have connected one of my MS600 to the 861 and then the system works fine.

If you connect the MS600 via SpeakerLink the 861 behaves very strange, but using an ID41 together with a MS600 is a strange combination.

861v8+ID41, HD621, G98, Arcam P35, DSP7200SE, DSP7200HC, SW1600, DSP320.
2xMS600, 2xMS200, 2xDSP3200, AC200, Explorer2, 2x218, AD88, Prime, 251, 210