Where were the photos sourced from .... a camera, or are they scanned photos where they were loaded directly onto the card from a hard drive via a a USB card reader
Are you trying to load the photos onto your hard drive from a camera .... or USB card reader?
If the card you are using was loaded directly from a hard drive and you are using a digi camera to loaded them back onto a hard drive you will encounter a format error, the same error will happen if the photos are sourced from a different model of camera that you are trying to load them with.
If you have taken a bunch of photos on a digi camera and suddenly you encounter a format error .... my experience is that you are pretty well SOL .... with that in saying I haven't experienced that type of error since way back on the earlier models of digi cameras.