WP Admin jumps to website

Hi,

I just bought a domain name http://www.nutrisian.com and it is hosted at Hostgator.

I used their cPanel > Fantastico to install WordPress. The main site is http://nutrisian.com. The admin site is http://nutrisian.com/wp-admin/ , according to the email sent.

However the problem is when I log in to the admin site, it jumps back to http://nutrisian.com. There is no dashboard, no admin portal. Please help me. What could be the problem?