rpc server is unavailable :(

hi I have a pdc running server 2003 runs fine on the subnet on which
it is located , but i now have to bring half a dozen machines into the
domain from another subnet and they cannot join the domain. I keep
getting the above rpc server unavailable error which has me a bit lost
as everything works fine on the same subnet I am suspect as to wether
this is a configurational issue or an issue with the cisco routers
blocking something although the unix gurus tell me nothing is wrong on
there end and that you have no prob with joining unix domains across
subnets hehe (not very helpfull). any suggestions would be greatly
appreciated

running dcdiag on another workstation on the servers subnet results in
every test passing but running it on the new subnet im trying to bring
in gives me errors like the following...

Domain Controller Diagnosis

Performing initial setup:
*** Warning: could not confirm the identity of this server in
the directory versus the names returned by DNS servers.
If there are problems accessing this directory server then
you may need to check that this server is correctly
registered
with DNS
[mydomain.edu.au] Directory Binding Error 1722:
Win32 Error 1722
This may limit some of the tests that can be performed.
Done gathering initial info.