The Beosound Ouverture was the first Masterlink music system and the LCS9000 with software version 1.0 was actually shipped with MCL enabled, but could be changed to Masterlink. Whilst the unit worked perfectly with MCL it had some flaws in Masterlink mode running version 1.0. Some commands would not correctly work and/or some could stop it from working/hang, I suggest this latter issue is what is happening to you.
I suggest you update your LCS9000 to version 2.1 software which will effectively make it a full Beolab 3500
There is an FAQ overview HERE which will give you more information.
About 18 months ago I produced a more detailed document which you can download HERE