Question : SBS 2003 drops *most* Internet connections every three hours

Currently running SBS 2003 Premium SP2 (but not ISA) with the following tweaks:
1) POP3 Connector
2) side by side upgrade to WSS 3.0
3) Trend Micro CSM SMB 3.0 with their Peronsal Firewall disabled
4) Windows Defender (service currently disabled)
5) Linksys router with all outbound ports open, very few inbound ports open.

We've run the POP3 Connector for over a year now without issue.  I don't he is is the culprit, just the messenger.  

Here's what's changed in the last few days:
1) We installed the most recent Microsoft patches. Did not seem to cause the problem.
2) We did a side by side upgrade of WSS 3.0 on our SBS Server.  Shortly thereafter the problems started.

Here is what happens:
After clean reboot all is well:
1) POP3 Connector wakes up and grabs email every fifteen minutes.  Full logging reveals all email is reaching its destination mailboxes
2) I can browse the Internet from the server.
3) I can telnet to my ISP's mail server
4) I can ping my ISP's remote mail server
5) Event logs reveal no problems, all info, no warnings, no red.
6) I can browse my new and old WSS sites from several clients.
7) Everything just runs fast the way its supposed to.

---After about three hours we do not lose Internet connectivity from the clients, but the Event Log starts to log lots of red errors because the POP3 Connector cannot connect.  Error:
Event Type:      Error
Event Source:      POP3 Connector
Event Category:      Download
Event ID:      1036
Date:            8/27/2007
Time:            7:31:19 AM
User:            N/A
Computer:      THE-SVR-2
Description:
An error occurred during a POP3 transaction to server . The error is 10060 (A connection attempt failed because the connected party did not properly respond after a period of time, or established connection failed because connected host has failed to respond.
).

---Next, a simple web page that calls to an EXTERNAL web service dies because it cannot connect.
Exception Details: System.Net.Sockets.SocketException: A connection attempt failed because the connected party did not properly respond after a period of time, or established connection failed because connected host has failed to respond.

---I can no longer telnet to my ISP's mail server

---I CAN ping my ISP's mail server

My original theory was that Trend Micro or Defender did not like something and shut down all outbound ports to prevent an outbreak.  Defender is disabled and I cannot find any issues with Trend Micro.

Event Log does not reveal any helpful messages, just that the POP3 Connector no longer connects and the ASP.NET error cited above.

How do I debug this situation?  This is our primary SBS production server and really need some help.
Thanks!
Keith

Answer : SBS 2003 drops *most* Internet connections every three hours

that Trend Micro product---is that Client Server Messaging for Small Business?  i'm really thinking that something in there may be the issue.