Longhorn Server and Vista communication problem

I'm having an issue with my Server 2008 and vista systems not being able to
communicate with my 2003 server. If I try and ping the address I get a
responce from my local system saying that the destination host is
unreachable.
Example:
Pinging 192.168.1.6 with 32 bytes of data:
Reply from 192.168.1.107: Destination host unreachable.
Reply from 192.168.1.107: Destination host unreachable.

Testing with a 2nd NIC in the 2003 server I created a 2nd IP for it to see
what would happen. I had no problems communicating with the system.
I have no issues with any other systems communicating with the server, XP,
2000, *nix all have no issues.

I just figured out this morning that if I add an arp entry manually to the
longhorn/vista systems for the server that communication works fine.
Anyone have any ideas what is causing this problem?