glue record question

[Joel Uckelman]

I think I have my DNS problems nearly settled (thanks, everybody). Just one 
more question: I was talking to register.com's tech support just a bit ago 
to get them to change the glue record for my name server from an incorrect 
IP at which it points now to the IP I'm actually using. The guy I was 
talking with told me that since there is already a glue record (for a 
different domain, which also happens to be mine) for that particular IP, he 
couldn't make the change.

For example, say the root servers for .foo have an A record for 
ns.example.foo:

ns.example.foo. IN A 192.0.0.1

And the root servers for .bar have an A record for ns.example.bar:

ns.example.bar. IN A 192.0.0.1

The claim made by the guy I was talking with is essentially that this is an 
illegal situation. So what's the problem with this? Is he right?

-- 
J.