Is it an option for you to backup everything on the HDD onto a PC, then reformat the HDD and put the games back on it? I know, I know... if you have a lot of games on the HDD, it could take a while. However, if there is an error in the file system, this could resolve it. Not only that, but if the games are on a PC, you can change over to fat32 from my signature, but this is not a fast process. It is, however, the only thing I can think of. Other then "did you plug the HDD into the correct USB slot?"