Outlook 2002 – Mail does not automatically appear

There is a PC connected to an Windows 2000 SBS Server with Exchange Server 2000. Outlook recieves emails from the Exchange Server. On this particular pc any messages coming in do not automatically show up, to get the new messages i have to click on the inbox or open an old message, the new message(s) then arrive in the mail box. I have compared the settings with other machines that are working fine with Exchange and they are the same. I have un-installed and re-installed outlook – i think it is a synconisation issue but im not sure. Please help!

Regards,
Tim.