The only thing I can add (and maybe this is a factor which the dealer didn't mention to you) is the early ML's AAM can only go up to 8 total keys. Maybe they realize the 2 remote keys are junk, but they checked the AAM and found you are out of keys (all 8 have been used). In that case you'd need more than the AAM, you'd also need the engine control module and you might even have to rekey the whole truck (new metal blades and lock cylinders) (not sure about that part though, but for sure a new engine control module and AAM).
Gilly

Problem Solved Update
 

Hey Gilly, and all - you were right! Brought the car to a different dealer and they determined the AAM is fine, and the two remote key's just crapped out for no known reason - They confirm what you said about all the keys having the same chip, so that's why my valet key works. I am wondering if the remotes got "zapped" on trying to jump the car, because those were the keys being used during charging and changing my battery - any theories?

The good news is, I just need to get a new remote, and not spend $500+ for an AAM and keys!

THANKS!

Very disappointed that the first dealer couldn't determine this.

No real good theory, but the reason I thought this might have been the problem is that the ML keys just haven't proven to be the most rugged. They just fail quite a bit. Supposed to be especially prone to damage after being dropped.
Kind of reminds me of this one kid (college kids, I call them "kids" generically) with I think it was a C class new enough to have a Smartkey. Standing around the service entrance, waiting for the service writer I imagine. Has the keys in his hands (DUH why even pull the key, you're standing by the car in the service entrance, I THINK it's safe to leave the key in!) and anyways was like "tossing" the keys up and down in his hand. Now, I don't know the level of this kids motor skills, but one think I DO know is that if you're tossing your keys up and down, you MIGHT not want to stand on the floor drain. Uh huh, RIGHT into the floor drain, and this was a BIG honkin drain too, probably 10 feet deep and 3 or 4 feet across. PLOOP!

Gilly