I just tried to import 40 photos I took today into Lightroom It told me that 8 of them (including the cutest one) were "Previously Added." Right clicking revealed "Import This" and "Show in Finder." Show in Finder takes me to the card, and Import This does nothing.
Let me reiterate, I took the card from the camera and put it in the computer. The images are similar, but taken each several seconds apart.