New Domain Log-in Problem

Hi!!

I bought a new domain some three days ago, and it was now activated. Now I can access my site through 3 different url. http://gptpinoy.darkbb.com, http://gptnetwork.com, and www.gptnetwork.com.

Problem is, I have links webbing my site. I was configuring my the links to the new url when I notice that when you jump from one domain to another, you have to log-in again. Which is quite bothersome.

I was wondering if there's a way to configure it in such a way that no matter what url they access they will be redirected to a consistent domain.

And another thing, I kept on disconnecting on my admin panel on the new domain.

PS. I notice that when I get disconnected from the admin panel, I am also disconnected from the site.

Anybody who can help?

Its quite useless to have a new domain if you keep on getting disconnected.