Outlook 2007 Doesn't Show Emails Until I Search For Them

Outlook 2007 (on Windows XP SP 2running ESET Smart Security and Windows Desktop Search ) doesn't show all POP3 messages downloaded from the server when doing a Send/Receive. If I search for the sender using Windows Desktop Search, most of the time I can find the missing email message. Then when I exit the search the message appears in the Outlook 2007 message pane.

Outlook 2007 is configured with 15 POP3 email accounts, most of them on different POP3 servers, including Gmail's. I usually get Gmail emails in Outlook without a problem. But sometimes an individual non-SPAM email from Gmail doesn't get downloaded (it cannot be found using Windows Desktop Search). This also happens with other POP3 servers.

Sometimes I can also get missing messages to appear by clicking on the calendar tab and then clicking on the Mail tab again.

Because of the speed of finding the missing emails by either means and their "magic" appearance, I'm fairly confident that the messages have been downloaded in Outlook but they don's show in the message pane (also since Windows Desktop Search can find the missing messages on my system they must be on my computer). lf I disable the Firewall, I still have this problem. In addition, ESET Smart Security includes anti-spam protection but the missing messages are not tagged as SPAM, while SPAM messages are.

Thanks for your help.