Firewall/NAT

I've followed http://doc.m0n0.ch/handbook/examples.html#id2603650 to the letter, however whenever I go to whatismyip.com from behind the DMZ i'm still showing the IP address on the WAN port rather than the IP address from the 1:1 NAT/DMZ.

What are some suggestions?

I saw some references to waiting out for a proxy arp cache to clear...  If anyone knows about this can you explain?  is there anything i can do to manually clear this cache?

If it were ARP, it wouldn't work at all, not show the wrong IP. Your 1:1 NAT rule has to be wrong if it's showing the wrong IP.