Java Thread becomes idle without any reason

I have a lot of troubles with following problem. Any hints are
welcome!
On one Netware server in  Netware 6.0 SP 5. Java 1.4.2 Thread in java
application becomes idle.
It happens only on this one server.
This thread is responsible for sending requests to GroupWise webaccess
and asking about current state of GroupWise mailbox.
Every user has one thread which is a part of java Bean in the Tomcat
web application.
It runs in infinite loop with one boolean in a while loop . This
boolean is set to false only if demo period expires.
If the JAVA Beans receives requests from mobile device everything is
OK and thread runs. But when no requests from the outside are received
then the  java Thread becomes idle after 10 - 15 minutes or less.
The result of this is "401 Authorization required" error in the
expired  http session with webaccess. It is possible to "resuscitate"
the thread when it is dying sending requests  to the application -
then he wakes up and starts to work.
I have studied thoroughly errors and exceptions from logs but no
caught or uncaught  exception can't be pointed as a cause.
I have no data concerning memory size of the server and  the traffic.
Best regards



Tomasz Cwietkowski