DNS Setup problem

Hi,
I've been working on setting up a server at home and am running into some issues resolving DNS for my site. Im running windows server 2008 and have a split DNS setup. I have a DrayTek Vigor 2920n with 5 static IPs.

Network config:
- Internal Domain Controller
- External Domain Controller
- Read-Only external Domain Controller in DMZ on IP #2
- IIS Web Server on IP #3 with port forwarding for 80/443

All is working except DNS resolution.
intodns.com reports that my RODC on IP #2 didn't respond (contains DNS entries for ns1 and ns2 for mydomain.com). I can ping IP #2 succesfully. If I get on the RODC VM I can ping out but can't browse (at first I couldn't even ping out but enabling recursion on the external DC fixed that). It seems strange that I can ping but not browse. If I take the RODC out of the DMZ I am able to browse. I suspect that when browsing in the DMZ perhaps the identified IP is IP #1 instead of IP #2 and the response is not able to find its way back? I'm really at a loss as to what could be going on.

All help is appriciated!