MDB and Websphere MQ Errors

[eefa]

Hi,

I'm getting some errors in my MDBs regarding missing PoolManager
references. I've done numerous web searches but I can't find an answer
to what is causing my problem. I'm working Websphere 5.1 and Websphere
MQ.

I make a number of successful calls, and then after a while calls start
failing, apparently when the beans attempt to place response on queue
when my code calls sender.send(response) a JMSException is thrown. I
extract the linked exception which is:
Linked exception:
com.ibm.mq.MQException: MQJE001: Completion Code 2, Reason 2102
at com.ibm.mq.MQQueue.putMsg2(MQQueue.java:1364)
at com.ibm.mq.jms.MQQueueSender.sendInternal(MQQueueSender.java:796)
at com.ibm.mq.jms.MQQueueSender.send(MQQueueSender.java:232)
at com.ibm.mq.jms.MQQueueSender.send(MQQueueSender.java:265)
at
com.ibm.ejs.jms.JMSQueueSenderHandle.send(JMSQueueSenderHandle.java:
Further down
java.lang.IllegalStateException: Internal Error: cannot find the
PoolManager Reference. at
com.ibm.ejs.j2c.ConnectionManager.allocateMCWrapper(ConnectionManager.java:640)
at
com.ibm.ejs.j2c.ConnectionManager.associateConnection(ConnectionManager.java:1383)
at
com.ibm.ejs.jms.JMSSessionHandle.getOpenSession(JMSSessionHandle.java(Compiled
Code))
at
com.ibm.ejs.jms.JMSQueueSessionHandle.getOpenQueueSession(JMSQueueSessionHandle.java:405)
at
com.ibm.ejs.jms.JMSQueueSenderHandle.<init>(JMSQueueSenderHandle.java:83)
at
com.ibm.ejs.jms.JMSQueueSessionHandle.createSender(JMSQueueSessionHandle.java:229)
...

In what scenario where would the PoolManager reference not be found?
Is this in some way related to configuration of connection/session
pools of my queue connection factories? I haven't modified these
settings in a while so I don't see how this can be the problem.

Any help is appreciated.
Thanks,
Aoife