Outlook not showing new messages unless it is restarted
I have only two Outlook users here. Both are on OL2003, with ZCO 5.0.2. The server is ZCS 5.0.9 NE on CentOS 4. What happens with these users is that after some period of time, they will stop seeing new messages appear in their inbox, even if they click on Send/Receive. If they shut down Outlook - which often requires killing outlook.exe from Task Manager or even rebooting - and then start it again, the new messages will suddenly appear and all will be well again for a few hours. Both of the affected machines are running on XP SP3, with Office SP3, and the problem has been happening for a long time.
Our other users are connecting via IMAP using TB2 and OE6 and never have such problems.
Is this a familiar scenario to anyone? Is it possible that this is being caused by ZCO? What additional information could I provide to help diagnose the problem?
Any advice would be appreciated.
Thanks in advance.