Consumer queues of virtual topic and the web console

We are using the stock ActiveMQ 5.10.0 configuration (with minor
modifications for JMX). With this configuration we have run into a very
strange issue every now and then with messages not being dispatched from the
consumer queues of a virtual topic until we click 'browse' on the web
console of that queue! On clicking browse, a flood of message is received by
the consumers and then nothing. This problem, seemingly, pops up randomly
and is not rectified until we restart ActiveMQ. What could explain this
behaviour?

On restarting the ActiveMQ service, the message dispatch returns to normal
and stays that way for some time.

The destinationPolicy configuration is (from the vanilla 5.10 setup):

<destinationPolicy>
<policyMap>
<policyEntries>
<policyEntry topic=">" >

<pendingMessageLimitStrategy>
<constantPendingMessageLimitStrategy limit="1000"/>
</pendingMessageLimitStrategy>
</policyEntry>
</policyEntries>
</policyMap>
</destinationPolicy>

We use Apache Camel for routing with the ActiveMQComponent (and a
org.apache.activemq.pool.PooledConnectionFactory). The activemq client
version is 5.5 (is this a problem?).

Thanks for any and all pointers!