Might need to post your config but a few things to check. Your vlan interfaces are based of your native lan interface? ie... eth1 (lan)... eth1.30 (vlan30) and eth1.40 (vlan40)
Also unrelated but you know you can give your vlans local dns if you add them to the dns forwarding under the services tab. ie... vlan30 dns 192.168.30.1
