I have an ad that shows only through AOL.com search and not Google.com...
The only thing that occurs to me is that your ad is actually showing in the (much coveted!) Premium spots 'up north' - and that you aren't used to looking for it there.
If you don't see it there, well, you've got me stumped. I'd suggest contacting AdWords support, as this sounds like a case where the account details would be important to see.
AWA
We were hudreds of visitors from AOL per day, and today it was 2.
chewy, a couple of things occur to me:
* Ad stopped showing on AOL because an edit was made to the ad. This'll pull it from partner sites until it can be reviewed & approved.
* A competitor has improved their position, and has moved your ad down (and out of the runnning) for some of your more popular keywords.
AWA