UPDATE:
Using the procedure in the owner's manual, I reprogrammed the fobs and they now work, but not like they did before.
Before, one press of the lock button would lock the doors and flash the lights. Two presses of the lock button would lock the doors, flash the lights, and chirp the horn ONCE.
Now, one press locks the doors. No lights.
Two presses locks the doors, NO lights and the horn chirps three times.
PLUS - now my headlights (only, no other lights) are on dimly when ever the key is in the ignition. It didn't used to do that. They are not on fully, just about half regular brightness.
I don't like my headlights being on all the time.
Any ideas?
Thanks.
Have your favorite tech hook up a diagnostic reader-to make sure that you aren't pulling any codes. It sounds like something additional-outside of deprogrammed/reprogrammed fobs is happening too...
yesterday I decided to attempt to adjust the passenger door reveal. I was successful at that 
-that the passenger airbag "off" light was lit on the dashboard-for some unknown reason) And I made that adjustment to the latch-as I said...
My pea brain wants to connect these two separate things-as to why my fobs deprogrammed themselves-cuz they did for no known reason, suddenly. OK-so I get the manual out-in the driveway-and I am NOT able to reprogram either keyless fob. I give up. This morning I unlock the car-old school-with the key. I get to work. I turn the car off. I decide for "grins" to try the fob-it works!
So I try the programming sequence-and reprogram both fobs on the spot.. WOW! The aliens attacked my Mustang and put an alien whammy on the computer. I'm just going to keep an eye out and-find my ray gun-in the meantime...
