I get a lot of ERRORs in jboss server.log,

2005-07-24 16:39:28,625 ERROR [org.jboss.ejb.plugins.LogInterceptor] TransactionRolledbackException, causedBy:
java.lang.IllegalStateException: A CMR collection may only be used within the transction in which it was created
at org.jboss.ejb.plugins.cmp.jdbc.bridge.RelationSet.getIdList(RelationSet.java:61)
at org.jboss.ejb.plugins.cmp.jdbc.bridge.RelationSet.size(RelationSet.java:68)

I have to restart my jboss if those errors occured, any ideas, thx!
I use jboss 3.2.1 with jetty, the server side is SLSB( session facade) + CMP2, all ejb methods transaction set

<trans-attribute>Required</trans-attribute>