w2k3 DC can’t see any other subnets

Finally got some new hardware in and decided to upgrade to w2k3 PDC. Built up the new server as a backup dns then went through all the migration steps to get the server ready. Everything seemed to go ok no errors or anything. We then switched the new 2k3 server over to the old servers’ IP/name. Then come to find out that the 2 other subnets we have can’t ping the new server. The new DC can ping any thing on its subnet but nothing on the other 2.
I’ve checked all dns entries and the enable netbios over TCP/IP settings. at a lost where to go next any help would be great!