Can't remember really if Miami3.x supports DHCP, but Miami Deluxe supports it, and i'm using it. I also used Miami Deluxe and my PCMCIA ethernet card to go online and surf the net. DHCP worked fine, you even can configure a static ip in Miami and it still works. Just be sure you put the DNS Servers in Miami database! Else you are online but can't browse the net and such.
Try to use these:
194.159.73.136 and 194.159.73.137
If Miami3.x doesn't support DHCP, then just type in a static ip in Miami Interface section. Check your modems manual for the ip gateway. Some use a number like 192.168.0.1 and others use different ip's. Mine uses 10.0.0.2 as the default gateway. And the modems built in DHCP range sets 10.0.0.1 till 10.0.0.15 as reserved. So i put a static ip as 10.0.0.16 in MiamiDx. And it works.
But still i guess it's the DNS Servers problem you have there. :-)