ConcurrentModificationException thrown in EventListenersContainerImpl

Saw this in my site logs:

SITE 2010-03-16 15:24:17,120 INFO [org.springframework.beans.factory.support.DefaultListableBeanFactory] Pre-instantiating singletons in org.springframework.beans.factory.support.DefaultListableBeanFactory@10f2591: defining beans containerComponentManager,javax.jcr.Repository,org.hippoecm.hst.core.jcr.EventListenersContainer,org.springframework.beans.factory.config.MethodInvokingFactoryBean#0,org.springframework.beans.factory.config.MethodInvokingFactoryBean#1; root of factory hierarchy
Exception in thread "EventListenersContainerSessionChecker" java.util.ConcurrentModificationException
at java.util.AbstractList$Itr.checkForComodification(AbstractList.java:372)
at java.util.AbstractList$Itr.next(AbstractList.java:343)
at org.hippoecm.hst.core.jcr.EventListenersContainerImpl.doInit(EventListenersContainerImpl.java:111)
at org.hippoecm.hst.core.jcr.EventListenersContainerImpl$EventListenersContainerSessionChecker.run(EventListenersContainerImpl.java:220)