Problem logging in after changing removing "www" in preferred domain

[asiaphoto]

I'm starting to have login problems after i'v changed my preferred domain from " http://www.asiaphoto.com " to " http://asiaphoto.com " instead.

i set up redirects in my .htaccess ( 301 ) to redirect surfers going to www.asiaphoto.com to access " http://asiaphoto.com "


I was unable to log in as a user or adminstrator at all in my forum
http://www.asiaphoto.com/forum.php

if i try to log in from the main page
http://www.asiaphoto.com/forum.php
i'll just get redirected back to the page not logged in

but if i try to log in from the admin panel
http://www.asiaphoto.com/admincp
i get a failed attempt #x of 5 allowed attempts



in my current situation, i can't even log in as administrator, otherwise i can configure AdminCP > Options > Settings > Cookies and HTTP Header Options > Cookie Domain?

what should i do?

reset my .htaccess to revert back the preference to www ?