Switching subnets within a domain

We have two small branch offices with are part of our NT domain, but each has a seperate subnet and are connected to the main office via T1 lines. We are running DHCP with a BDC in each of the branch offices.

When users move their laptops fromone office to another, they do not pick up a new IP address for the new subnet unless they have administrator rights. Also, they cannot use the commands IPCONFIG /RELESEASE or IPCONFIG /RENEW unless they have administrator rights. Where should I be looking to correct the is problem? It appears that the WINS databases are not replicating between the locations. Could this be the problem? HELP