I didn't realize MyBook's had a sleep function. Not sure if mine does or not. I had actually planned on getting a new external disk, but when I checked at our local Staples they didn't have anything with eSATA, just USB2/3. Seems to be less common now. Instead I bought a new MyBook for my PC and used the old MyBook with eSATA on the DVR. As I mentioned I had the replace the original disk as well, but it's possible that the 1TB Seagate disk I got is the issue. I'm going to play with a couple of smaller 300GB disks not being used and see what kind of results I get.
Thanks for the info!