Cisco Pix Failover Upgrade

Ran into a small issue with a PIX upgrade:

2 Pixes running 6.3.3 configured for failover, with config synced.

Upgraded the standby box to 6.3.5 and rebooted. The active box remained active and took down the failover since the OS version was not matching any more (6.3.3 vs 6.3.5).

Then upgraded the active PIX and when it rebooted the standby took over. When the original active PIX came back up though the 2 pixes started fighting over who was the active PIX and the public and inside ips would switch back and forth between the boxes as the battled to take over.

Rebooting the backup PIX fixed the issue, and then a write mem and write standby from the active PIX once the standby came back up showed that the config was able to be synced from active to standby properly.

Here is a status from the active pix when failover is working properly.

fw# sh failover
Failover On
Cable status: Normal
Reconnect timeout 0:00:00
Poll frequency 15 seconds
failover replication http
This host: Primary - Active

This host: Primary - Active
Active time: 1395 (sec)
Interface outside (a.b.c.157): Normal
Interface inside (192.168.x.3): Normal

Other host: Secondary - Standby
Active time: 0 (sec)
Interface outside (a.b.c.153): Normal
Interface inside (192.168.x.4): Normal