Steve,
The PB (Primary Backup) state is normal -- http://kb.juniper.net/InfoCenter/index?page=content&id=KB5124&actp=search. All backup firewalls I've ever seen are in PB state. (With secondary interface via L2 device enabled.)
The first link you included seems to point to an article that's in review and is not visible.
Lastly, I believe OP is referring to the Alarm LED, not the HA LED. My observation is that the Alarm LED will come on any time an alarm-level event (or higher) shows up in the log, and the LED will remain lit up red while the log contains those messages, even if whatever problem said messages refer to has been resolved.
- Nikolay