OpenJMS crashing! Help!

Hello
I am running the server in non persistent, tcp mode.

Here is what I see when I have around 50 publishers and subscribers to
same/multiple topics.
Can someone tell me if there is a configuration piece I missed and why this
is happenning? This is not like the server is running for days.. it
happenned in just an hour of all the publishers/subscribers coming in.

15:26:18.968 ERROR [Scheduler-Worker-2] - javax.jms.JMSException: Could not
get message for handle Handle : 4:1059159614031:3267
:ID:6202634392488269420
javax.jms.JMSException: Could not get message for handle Handle :
4:1059159614031:3267:ID:6202634392488269420
        at org.exolab.jms.server.JmsServerSession.onMessage(Unknown Source)
        at org.exolab.jms.messagemgr.TopicConsumerEndpoint.run(Unknown
Source)
        at
org.exolab.core.threadPool.ThreadPoolWorker.runIt(ThreadPoolWorker.java:186)
        at
org.exolab.core.threadPool.ThreadPoolWorker.runWork(ThreadPoolWorker.java:17
3)
        at
org.exolab.core.threadPool.ThreadPoolWorker.access$000(ThreadPoolWorker.java
:67)
        at
org.exolab.core.threadPool.ThreadPoolWorker$1.run(ThreadPoolWorker.java:117)
        at java.lang.Thread.run(Thread.java:536)


after a period of time I start seeing this:

java.lang.OutOfMemoryError
java.lang.OutOfMemoryError
java.lang.OutOfMemoryError15:52:34.031 INFO  [EventManager-Worker-3] -
Failed to verify that session 976118066399111786 is active.

Thanks
Ivy