Hello, I just purchased a 160GB Western Digital My Passport external HD to use with time machine. Every time i attempt to back up I get the following message. TIME MACHINE ERROR Unable to complete backup. An error occurred while copying files to the backup volume. This always happens when the back up reaches 7.74 GB. I have used the Disk utility repair feature on my hard drive and also re-formated the back up, but I am still having problems. Any suggestions to help? Should I return this hard drive and get a new one? Let me know- thanks!