Windows 2003

I'm going to be configuring my new server as an email and DNS server within a
DMZ. Currently, I have the email and DNS settings configured but I have all
of the services turned off.

First off, when I allow my new server to plug into the network, it plays
games with the network. I cannot ping another server on my network correctly
- When I ping 192.168.3.7, I get ping responses back from the new server
(192.168.8.11). The source is 192.168.8.11 and the destination reply comes
from 192.168.8.11!

Secondly, when I plug in the new server, I cannot receive email from an
internal mail server (192.168.8.10) from the 192.168.3.7 machine.

Everything has worked for the longest time. The only time it doesn't work
is when I plug in the new server. When I unplug it from the network,
everthing goes back to normal in about 10 minutes or so. I'm pulling my hair
out on this one and have even resorted to sniffing the traffic with no
resolution yet...

Any help would be appreciated...