Tacacs servers moved to a new subnet. Changed the AAA and telnet statements on the PIX to point towards and allow the new servers.
Egg on my face, when I couldn't log into the PIX. Checked syslog and saw that there was no route configured to the new subnet. Doh!!
I realized that a 'route inside' statement was missing. I attached console cable to the PIX. Console access requested Tacacs credentials.
Need assistance on how to add the "route inside" statement without bringing down my firewall. Firewall is also in failover configuration.