This was a Discover Card rep calling to tell me that an auto-payment to my card balance had failed to go through. I figured it was a scam and that she was going to ask for bank account or other private info, so I logged into my online account to check. It turned out she was correct. I told her I'd take care of it through the Discover Card website and she said ok. I believe this call was legitimate.
Readers:
Be Safe, Not Sorry
Rather than believe the posts in this thread, or the words of an anonymous caller,
if you are notified of a problem with your card,
CALL THE NUMBER ON THE BACK OF YOUR CARD
Even though the number in this thread might belong to your card issuer, the scammers can easily spoof what appears on your CallerID, and attempt to get your precious ID and card data!