Invalid TLD when setting nameserver.

[Duncan]

I purchased a domain name from GoDaddy.com, I want set the nameservers to 
point to my primary DNS that I set up, I am using twisted4life as my 
secondary, My primary is successfully transfering zone data to the 
secondary. But when I try to set the nameservers, I get the error message, 
"Nameserver 1 has invalid TLD.", nameserver 1 by the way is the IP of my 
primary that is on my machine. I am running the DNS server on a Windows 2003 
system with no Active Directory installed at the moment. This is all 
experimental at the moment, im new to DNS, can anyone tell me if I am making 
any obvious errors that would cause my promblem?