Hmmm... spoke too soon - I wasn't sure yesterday, could have been something else, but now it is 2 days in a row where it isn't picking up my POP email correctly.
What I mean: I use Windows "Hibernate" at the end of each day, and then come back from that the next day. I am now seeing 3 separate but possibly related issues:
1) the usual "Check for new messages every 5 minutes" per-server email settings are not "coming back" when Windows is restored from the Hibernate - this has *always* worked with all previous SeaMonkeys, but was obviously not working, as I cannot turn on my computer in the morning without new email being present
2) the "Get new messages" UI function used to default to "across ALL email accounts", now it seemed to just get the first entry, so I had to explicitly force this on my other account(s)
3) In fact, the regular "probes" of the POP servers (one "real", one the GMail simulated one) are not continuing at all - even after attempting to "kickstart" things - this was apparently masked yesterday by my stopping and restarting the SeaMonkey app
Let me know if there is anything I can check for or questions I can answer.
Edit: I have now confirmed that restarting SeaMonkey is both necessary and sufficient, in order to restore the automatic checking of all (both) my POP email accounts... the "Get new messages" button behavior is still now at this reduced functionality, defaulting to only the first of my two POP servers, rather than as before, defaulting to the "Get All New Messages" menu entry.