is your domain fresh off the presses? it can take time for DNS servers to update which is beyond DH's control. that can take anywhere from 5 minutes to several days.
if you are in a hurry, you can create an SSH tunnel and forward port 80. I think this would work, although I haven't tried. It also violates DH's TOS if you use that technique to surf the web in general. I assume that if you are using it to view your own site, it may be allowed.
any comments from andrewf or rparker on this?