Network Issue in Windows 2000 Server

I recently had some issues with networking in Windows 2000 Server and while I was able to troubleshoot and get things to work, I am at a loss to figure out why I am seeing the behavior that I am.

I have a Windows 2000 Server (Dell PowerEdge 650) that runs our card reader security system. The security system has a panel that has its own ethernet card connected to one of my servers network ports (#2). It is set up for a static IP address (192.168.100.2), subnet mask (255.255.255.0) and default gateway (192.168.100.1) for the security panels ethernet card. The other network port on my server (#1) is set up to obtain an IP address automatically from the network.

When I start up the server with both network ports active, my server cannot see a network DNS server that runs a script to map out shares on our network and one of my users cannot connet to the server using software that is meant to control the security system.

When I start up the server with the #2 port (going to the security panel) deactivated, my server sees the DNS server and runs the script that maps out all the network shares to drives on the server...of course the security port is deactivated so I have to reactivate it after logging on to the server. When I follow these steps, the security software works just fine.

It seems as though the #2 port (security system) is "blocking" my server from seeing the DNS server somehow and I'm not sure why. Anyone have any ideas?

Thanks