Has anyone else had this same problem and found a way to fix it? I just got a 1GB external hard drive a couple weeks ago and partitioned it into 2 500GB chunks. One of them is a backup for Time Machine which was going well for about a week until one day I started to get the message every hour "Time Machine Error: Unable to complete backup. An error occurred while copying files to the backup volume." The only thing I have done differently in the past week is updated my iMac to the latest firmware. Any ideas?