NPE in org.jboss.mq.server.BasicQueue.setupMessageAcknowledgement()

In a clustered system with 4 server instances, and after having received a couple of thousand of messages, we got the following exception in our logs. Afterwards, one subscribing MDB won't be called in onMessage() anymore. The stuff I wrote in the forum probably really is just unducated guessing.

2006-10-24 18:53:24,187 ERROR [UIL2(SocketManager.MsgPool@a52a72a client=192.168.100.214:53381)#4 SocketManager] Failed to handle: org.jboss.mq.il.uil2.msgs.ReceiveMsg2084258688[msgType: m_receive, msgID: -2147361440, error: null]
java.lang.NullPointerException
at org.jboss.mq.server.BasicQueue.setupMessageAcknowledgement(BasicQueue.java:945)
at org.jboss.mq.server.BasicQueue.receive(BasicQueue.java:516)
at org.jboss.mq.server.JMSTopic.receive(JMSTopic.java:320)
at org.jboss.mq.server.ClientConsumer.receive(ClientConsumer.java:222)
at org.jboss.mq.server.JMSDestinationManager.receive(JMSDestinationManager.java:656)
at org.jboss.mq.server.JMSServerInvoker.receive(JMSServerInvoker.java:226)
at org.jboss.mq.il.uil2.ServerSocketManagerHandler.handleMsg(ServerSocketManagerHandler.java:155)
at org.jboss.mq.il.uil2.SocketManager$ReadTask.handleMsg(SocketManager.java:369)
at org.jboss.mq.il.uil2.msgs.BaseMsg.run(BaseMsg.java:377)
at EDU.oswego.cs.dl.util.concurrent.PooledExecutor$Worker.run(PooledExecutor.java:748)
at java.lang.Thread.run(Thread.java:595)
2006-10-24 18:53:24,251 WARN [Connection Consumer for dest Subscription[subId=-2147483648connection=ConnectionToken:ID:23/null destination=TOPIC.sgw/MOCacheInvalidationTopic messageSelector=null Local Create] id=12 SpyConnectionConsumer] Connection consumer closing due to error in listening thread SpyConnectionConsumer[sub=Subscription[subId=-2147483648connection=ConnectionToken:ID:23/null destination=TOPIC.sgw/MOCacheInvalidationTopic messageSelector=null Local Create] messages=0 waitingForMessage=false internalThread=Thread[Connection Consumer for dest Subscription[subId=-2147483648connection=ConnectionToken:ID:23/null destination=TOPIC.sgw/MOCacheInvalidationTopic messageSelector=null Local Create] id=12,5,jboss] sessionPool=org.jboss.jms.asf.StdServerSessionPool@6c6fff7a connection=Connection@753785396[token=ConnectionToken:ID:23/null rcvstate=STARTED]]
org.jboss.mq.SpyJMSException: Cannot receive ; - nested throwable: (java.lang.NullPointerException)
at org.jboss.mq.SpyJMSException.getAsJMSException(SpyJMSException.java:66)
at org.jboss.mq.SpyJMSException.rethrowAsJMSException(SpyJMSException.java:51)
at org.jboss.mq.Connection.receive(Connection.java:916)
at org.jboss.mq.SpyConnectionConsumer.run(SpyConnectionConsumer.java:238)
at java.lang.Thread.run(Thread.java:595)
Caused by: java.lang.NullPointerException
at org.jboss.mq.server.BasicQueue.setupMessageAcknowledgement(BasicQueue.java:945)
at org.jboss.mq.server.BasicQueue.receive(BasicQueue.java:516)
at org.jboss.mq.server.JMSTopic.receive(JMSTopic.java:320)
at org.jboss.mq.server.ClientConsumer.receive(ClientConsumer.java:222)
at org.jboss.mq.server.JMSDestinationManager.receive(JMSDestinationManager.java:656)
at org.jboss.mq.server.JMSServerInvoker.receive(JMSServerInvoker.java:226)
at org.jboss.mq.il.uil2.ServerSocketManagerHandler.handleMsg(ServerSocketManagerHandler.java:155)
at org.jboss.mq.il.uil2.SocketManager$ReadTask.handleMsg(SocketManager.java:369)
at org.jboss.mq.il.uil2.msgs.BaseMsg.run(BaseMsg.java:377)
at EDU.oswego.cs.dl.util.concurrent.PooledExecutor$Worker.run(PooledExecutor.java:748)
... 1 more