com.sonicsw.xq.XQEndpointTimeoutException: Call timed-out

I have a very odd situation....

We are using making a web service invocation from an ESB process.  All is well except for one situation.  If we specify a certain set of parameters in the invocation, we receive: com.sonicsw.xq.XQEndpointTimeoutException: Call timed-out
    at com.sonicsw.xq.connector.jms.JMSEndpoint$EndpointConnection.callWithQoS(JMSEndpoint.java:1986)
    at com.sonicsw.xq.connector.jms.JMSEndpoint$EndpointConnection.syncWSInvokeWithQoS(JMSEndpoint.java:1836)
    at com.sonicsw.xq.connector.jms.JMSEndpoint.syncWSInvokeWithQoS(JMSEndpoint.java:306)
    at com.sonicsw.xqimpl.invkimpl.wsif.providers.axissoap.ESBJmsSender.invoke(ESBJmsSender.java:137)
    at org.apache.axis.client.AxisClient.invoke(AxisClient.java:165)
    at org.apache.axis.client.Call.invokeEngine(Call.java:2765)
    at org.apache.axis.client.Call.invoke(Call.java:2748)
    at org.apache.axis.client.Call.invoke(Call.java:1902)

To diganose the issue, I setup TCPMon.  The web service is returning, and the HTTP Connection is going to DONE in TCPMon, but the ws-invocation just hangs there.

Again, this is working for all other invocations of the web service.  And using TCPmon, I can see the web service invocation responds properly.

Any ideas why the process doesn't proceed?

thanks,

brian