Time Machine can no longer back up files
I was using Time Machine to back up files to a WD Elements hard drive. Lately I started to get error messages the back-up failed. Previously Finder would list back-up files for that drive, but now it only shows empty folders. Get Info still shows 60 GB of used space on the external drive. Can I retrieve those files, or is all lost and I must reformat the hard drive?
iMac, Mac OS X (10.6.8)