Well, that means that along the way somehow when you were backing up on the disc, the data got corrupted. Each data sent is given a CRC value and when it's corrupted along the way, the data and the CRC doesn't match; thus, it gives you the CRC error after many attemps to try and read the data.
However, all your data isn't lost (hopefully). Some steps you can try is to clean your disc drive and your disc and try again. If not, you might want to look into a recovery tool called CDCheck 3. Type it into google and it should be the first link, it's totally free.