Following troubleshooting steps might help
- unplug the secondary pix failover cable
- write erase secondary pix config
- reload secondary pix (at this point there should be no config on secondary
- configure basic secondary pix config as per following URL
http://www.cisco.com/warp/public/110/failover.html
http://www.cisco.com/univercd/cc/td/doc/product/iaabu/pix/pix_61/config/failover.htm
- save and shut down
- make sure all ethernet ports on primary and secondary are connected properly to the switch
- plug the failover cable back to secondary pix (ensure the secondary-end is plugged onto the secondary pix)
- boot the secondary pix.
- do a show failover at both ends
- issue a write standby command on the primary pix (to push config to secondary)
- verifiy configs on both pix
HTH
R/Yusuf