Pb with 2 IS wm 601 in cluster


 I try to put two IS in cluster mode on two different servers (server A and server B) and it seems to be Ok. But when I disconnect  IS A (stop IS A or disable network on server A ), the IS B froze. The IS B seems to be Ok but doesn't reply, i can't connect with any tool (WmAdmin, WmMonitor). When I start IS B, it seems to process messages but all process failed. (I used PRT with modeler) 

Do you have an idea of what happened ? Does someone use cluster ?