Recently I installed Vista beta 1 installation and was very anxious to see vista desktop . I got stuck on login screen and was getting error something like cannot connect to domain.
To resolve the problem, I unhooked the adsl modem from LAN card and remove the pci Lan card as well but it wasn't required I think.
I did fresh installation again and it worked for me.
Now I can login without any error.
Hope it helps!