Describe how you are connecting.
IMHO always use ethernet in complete isolation from the network.
Also if you upgraded to the latest no so greatest airport utility.. you must use ipv6 local-link for anything to show up.
see belated apple note. http://support.apple.com/kb/TS4597
Or you can use your ipad and the latest airport utility. often works better.
Factory reset rather than hard reset but it depends on what version you are talking about.
If none of the above work please give more info.
Model TC.. A1xxx from the label.
Network layout.. main modem? How the TC is connected both to the modem and the computer??