Sorted out the problem. Seems many people have the same problem.
What happen was that I run "yum update" and somehow it updated bind-chroot package and maybe changed the permission of the chroot folders. As in numerous other posts in the forum, the solution was to run the following command again. Hope it will help others who have the same problem.
chmod 755 /var/named/
chmod 775 /var/named/chroot/
chmod 775 /var/named/chroot/var/
chmod 775 /var/named/chroot/var/named/
chmod 775 /var/named/chroot/var/run/
chmod 777 /var/named/chroot/var/run/named/
ln -s ../../ chroot