Complete Backup freezes machine: hardware or software?

Hello
I'm running Vista 64 with 8 G Ram, 2 Tb sata hard drives.

Using Windows complete backup, I am backing up to an external drive with
options for either E-sata or usb connections . The external drive is
connected as an "E-sata" drive when the backup freezes on disk one 3rd
partition which happens to be an sql database (not running). If I turn
off the external drive, the system recovers and of course the backup fails.
The backup completes if I run the external drive on the USB interface.

Ok so my thinking is there is something wrong with the external drive using
the E-sata connection. I have the latest bios updates. I downloaded
Acronis 11 and repeated the same backup configuration as above and the
backup completes successfully on the external drive interfaced as E-sata.

Anyone, any ideas if the drive is faulty or its a bug in Vista?