Sounds pretty bad, I take it there is no way to copy the data on the harddrive? If you can copy all of the stuff off the hard drive might be worthwhile just formatting.
this happened to me last night but i had 2tb of data n i lost it all i spent hours trying to get it off but i had no luck
Looks like your drive has a bad sector or sectors,try running check disk.
In computer,right click on drive/properties/tools/under "error checking" select "check now"/
tick both boxes "automatically fix file system errors" and "scan for and attempt recovery of bad sectors/start.
maybe i should have made a backup of my backups on another backup drive.....