Your "sda" disk may have a single bad block. The harddisk manufacturers will tell you "that's normal".
What you can do now is to format the external drive with the same filesystems that you had, and then copy over the files.
Despite what everybody else says, cloning a system as you're trying should in principle work just fine, provided that your destination drive is the same size or bigger than the original drive. If the destination drive is bigger than the original it may leave you with some hard-to-use diskspace, but that's what you get if you clone a PC like that....
Last edited by rew; 11-04-2010 at 06:55 AM.