Latitude laptop not recognizing AC adapter, not charging

I have a Latitude E5550  running Windows 7 which is having this problem.  It has operated just fine since Feb 2015 when I bought it, until within the last 3 weeks when I got:

"The AC adapter wattage and type cannot be determined. The battery may not charge. The system will adjust the performance to match the power available. Please connect a Dell 65W AC adapter or greater for the best system performance."

At boot time, I get

"The AC power adapter wattage and type cannot be determined.
 The battery may not charge.
 The system will adjust the performance to match the power available.
 Please connect a Dell 65W AC adapter or greater for the best system performance.
 Strike the F3 key (before F1 or F2 key) if you do not want to see this power warning message again.
 Strike the F1 key to continue, F2 to run the setup utility."

The battery icon in the System tray shows "not charging" and a level of 94%.

The adapter for this laptop model does not have a status light.

NOTICE: This has happened twice. The first time I had the laptop  plugged into the AC adapter that came with it.  When it blew, I bought a new one from Dell. 

When I bought the new adapter, I swapped in each of the three sections one at a time.  I kept getting this message, until I swapped in the part that plugs into the surge protector on one end (with the ground pin) and into the adapter on the other end.  (the other two parts are the adapter itself, and the cable that plugs into the port on the laptop)

The second time, there was a power drop that turned off my lights and Internet router.   The router and lights recovered but I started getting the first message.  It seems to me that the first time  I had it,  the problem started after a similar power drop. I remember hearing the Internet router beep angrily.   IIRC the laptop was powered down this first time.

At one point I suspected that the  laptop  itself was causing power spikes because how would a grid problem get through the surge protector (which I also  bought from Dell)?  The surge protector has a green light on it and the "Ground" indicator is dark; it would be red if there were a problem with the ground, true?

There is a thread about this on the NotebookReview site but not for this model.  I tried blowing canned air into the adapter plug and into the laptop port -- no luck.  I haven't switched out any other hardware.

I have ordered another new adapter and made sure it was a 65W part.  It  should arrive about July 13.

If BIOS updates are working for other people, can you show me the  link  to a BIOS upgrade for the E5550?  Other ideas?

Thanks