Most likely you'll need to backup all your other playlists and format the hard drive to correct the error.

If you can get into the menu system, you can simply press Utility 8 times to go to Format Hard Disk, and select this option.

Remember, this will ERASE ALL YOUR DATA, so make sure you have backups of playlists or files you need before performing this operation.

If you have OS version 2.0 or higher, this procedure should not erase your operating system and you will not have to reload the OS from CD.