Linksys Wireless Router :: Cisco Pix 501 Doesn't Work After Being Unplugged

Trying to troubleshoot a Cisco Pix 501. We have a cable modem/router that goes to the Cisco box that then goes to my wife's computer. It's worked flawlessly since we hooked it up, even if we unplug/replug the router. Today, we unplugged the Cisco box itself to hook up a newer one. When the newer one didn't work, we tried to hook up the old one again to no avail. The led indicators seem to show that everything's working properly. We've unplugged and rebooted everything. Nothing works. The network monitor on the computer shows that it detects being connected to a network, but it always says no internet access.