@MrTom 

I ran v1.1.2 for a while and it didn't help.

The thing is, there's an old saying that goes "90% of all networking problems are cabling problems and 90% of the rest are configuration problems."  While your concern is understandable, it's unlikely that this is a firmware problem.  There are three pieces that I haven't ruled out:  The device itself, the PoE injector, and the cable where the cable is still the likely culprit.

Unfortunately, isolating the problem to a particular piece is going to require getting the ladder out and climbing up there to bring it down.  That has had to wait for the weekend because I don't have time during the week.  In a couple of days, I should know.

  @Vincent-TP 

The client-side wireless works great.  It is only the wired network that is the issue.  When you say "resetting the device" do you mean going to the System->Reboot/Reset and clicking on the "reset" button?  I've done that and I had a question about it, actually.  The only obvious result of resetting to factory defaults was removing the checkbox from the "Layer 3 Accessibility" of the web server, and disabling SSH access.  I was expecting other things to be reset, like the default password and the SSID for the 5 GHz Wireless Radio, and they weren't.  Is the behavior that I saw expected?

Anyway, resetting to factory defaults doesn't make the wired network work.  Alas.