Secondary Network Problems – winNT

I am using a Firebox III 700 as a DCHP for a subnet of the compnay network for Audio visual Equipment. these machines are in the range 10.0.6.x and the firebox is at 10.0.6.254.

1 machine is windows 2000 pro and the other two are windows NT4.0 workstations.

The win200 machine accepts the ip fine as does the other machines but my attempts to get them to join a workgroup have failied i cannot get them to resolve the domain names each has been given, this is required for media transfer.

any ideas?