Every couple hours, Tomcat stops

[Bruce]

I have an installation where Tomcat stops every couple hours.
   * Tomcat 6.0.18
   * Windows XP pro 2.3GHz, 2G memory
   * The application is in a .war file.
   * This app reads and writes to a MySQL database on the same machine.

What happens is that the application will run for about 3 hours or so. 
Suddenly, it stops responding. When that happens, the operator opens the 
"Config Tomcat" application (\Tomcat 6.0\bin\tomcat6w.exe) She then 
stops Tomcat and then re-starts Tomcat. And, Tomcat will run for another 
3 hours or so.

I went into server.xml and set connectionTimout="2000000" Tomcat still 
stops.

I have a dozen similar setups. None of them have this problem. In fact, 
Tomcat has run for months on some of the installations.

Does anyone know how to fix this problem?

Thanks in advance.

Bruce