When you transfer a domain name, the DNS settings from your old registrar
will be handed over with your domain to your new registrar. When your new
registrar gets the domains and you access them on their site, only then, will
they allow you to change the DNS settings.
This is a process that is made to avoid downtime completely.
Now, I will add the comment that not all registrars are created
equal..... Some may not adhere to the rules due to buggy programming
on their end, however if it is a larger company, then by all means it should
be ok. DomainNameSystems or DirectNic seem to be good along with godaddy.com
Happy Halloween!
http://www.seejack.com/viral/halloween1
http://www.seejack.com/viral/halloween2
Chris Jester
SplitInfinity Networks