Troubleshooting Tomcat because of an obvious threading issue

With our Java web application running Apache Tomcat 6.0.18 on Ubuntu with Java 1.6.0_6, we can shutdown tomcat completely.

However, with the same war file deployed in Apache Tomcat 6.0.18 on Red Hat Enterprise Linux with Java 1.6.0_13, the call /etc/init.d/tomcat6 stop

does not stop Tomcat. I have not tried using 1.6.0_6 on Red Hat yet to see what happens. Until I get any ideas there?

jstack shows no deadlocks. The webapp uses Spring 2.5.6 and JAX-WS to provide SOAP based web services, if that matters.

Thanks for the help.