Well, it apears like the browser service on DC1 is stopped, OR you are not maintaining a browselist on DC1.
Let's do some basics to make sure we don't overlook these things and we will progressively get harder into Netbios/Browser troubleshooting.
-Check to make sure these services are enabled:
-File and print sharing (on the NIC configuration)
-On the WINS tab of TCP/IP configurations (make sure netbios over TCP/IP is enabled)I
-In Services, make sure the Browser Service and Workstation service are started and set to automatic
-See if your firewall has been enabled. NOTE( if you enabled RRAS, then your firewall is enabled regardless of the service being set to disabled and not started)
I think we went to the command prompt and typed Net config redir to check the network director service to see what nic netbios is bound to, right??