Originally Posted by FearFree

I've had a card get declined on the first try, and work on subsequent tries. My card was fairly well worn, and the magnetic strip didn't read well. Some merchants it worked fine, other times it must have only read the partial numbers and at these places would come back as declined. A 2nd swipe often resulted in an approval, and if not a manual entry of the card number would always result in an approval. It wasn't usually a problem except for the one day at McDonald's when the cashier was adamant that she couldn't manually enter the numbers.

The card has since been replaced, but it is certainly plausible.