I have an exception when trying to write in cluster

I have a cluster of space on deployed on several hosts(machines). When I try to write something to cluster(no matter how I do that, it's both not working benchmark or even from my code ). But it work fine if I kill all machines and left only one in cluster. So, exception is: Exception occurred during Exception For more information press details: java.lang.ClassNotFoundException: class com.j_spaces.examples.benchmark.messages.MessagePOJO not found .... com.gigaspaces.internal.client.spaceproxy.operations.WriteEntrySpaceOperationRequest.readExternal(WriteEntrySpaceOperationRequest.java:180)