From your hda itself (via ssh or at the desktop in a terminal), can you:
# ping hda <small>(it should ping the IP of your HDA; this ensures the dns server is working)</small># ping router <small> (it should ping the IP of the router; this ensures your HDA can see the router)</small>
# ping 68.180.206.184 <small>(this ensures you can see the rest of the world)</small>
# ping yahoo.com <small> (this ensures your dns server can see the world)