Nameserver Issues

[TitaniumHosting]

I am trying to set up nameservers for a reseller client I have. However, when he tried to point a domain to them he gets an error saying something like:

ns1.********.com is not a valid nameserver.
ns2.********.com is not a valid nameserver.

Does anyone know what may be causing this?

[PWSowner]

Have the nameservers been registered at the domain registrar? If so, it may take a few hours to be public.