Can't login with custom domain


I have installed the domain mapping plugin and I am able to map an external domain to a sub blog of the multisite install. One thing though, when I try to login with the newly mapped domain, it keep redirecting me back to the login page.

for example,

i have mapped a domain to

When i go to, it doesn't me to login. Instead it keep redirecting me to the login screen.

Any help will be appreciated.