Lightroom reporting corrupted files
I store all my original photos on an external drive and now Lightroom reports some of them as being damaged or unreadable. If I find the individual files then they are not damaged and open OK in Photoshop. Ive tried rebuilding the Lightroom catalogue and also tried to copy the files from the drive to another drive but always get an error. Can anyone recommend a programme that will scan the drive and repair or quarantine any damaged files so that I can copy the rest off to another drive and format the original drive to start again. I do have a full backup but don't want to just format the originals just in case the backup then gets corrupted or fails. Any help appreciated.
External drive is a Drobo and drobo software reports no problem with the drive, am running a Mac Pro with 14gb Ram and 2 x 2.66 Dual core.