I have a 2007 H3. I purchased it new in late 07. I have 48,000 miles on it.

I was in the high altitude yesterday (10,000 feet) and after a long descent on a jeep trail in first gear I got to town (about 8,000 feet). In town I slowed put in into drive then headed thru town. I came to a stop light the RPMs started to jump from 0 to about 500. then the engine died.
I stopped restarted the engine, and it almost did the same thing until I accellerated.
I was only going a few miles so I continued. The engine almost died a few more times when I would stop at stoplights. as long as I accelerated I was fine, no loss of power at all. The problem only occored when I would slow down.. (full tank of gas, new air filter)
that was late last night, today the engine idles fine and I have had no problems....

What could have caused that, and is there a more serious underlying issue I should address???

 

Sound EGR or TB related to me. If it is good now, and you have no CEL, you're good to go. You could take a look at the TB, they get mighty cruddy at over 40K miles, and even worse if you feed them cheap gas.

look into some of this