[Zope] zope 2.8.5 becomes unresponsive.

Environment is RHEL 3, Zope v2.8.5 (Python 2.3.5). Every couple of days the zope instance will become unresponsive and require a restart. ZMI is inaccessible at these times so I have to do run "service my_zope_service restart" in the usual redhat way. There is nothing in the logs, and if I do "service y_zope_service status" I am told "program running; pid=22671" This is a service under very light load. I viewed the chanelog for v2.8.6 and didn't see any changes that address this, and for various reasons I do not want to move into the v2.9.x builds. Any guidance appreciated.