Windows 2003 NAT not working ...

Trend Micro Officescan can causes Windows 2003 NAT not working.

If you install Officescan client program into your Windows 2003 server,
the NAT function will stop immediately.

The solution is to remove Officescan client program from your Windows 2003 server.

One solution for free Anti-virus program on Windows 2003 is Clamwin, it can be
downloaded from http://www.clamwin.com/