Plugging the My Book directly into the wall socket resolved the issue
I received this from tech support
Thank you for contacting Western Digital Customer Service and Support. My name is Gustavo R.
I apologize for the inconvenience that you are experiencing, I have a few questions for you. Are you hooking up your external hard drive to a USB hub or extension cable? It is always recommend that you plug your external hard drive directly into your computer. Are you using the power adapter we supplied with your drive?
Do you plug your external hard drive’s A/C adapter into a power strip or directly into a wall socket? If you are using a power strip or battery backup then we recommend that you connect your hard drive directly into a wall socket. In the past, we have seen several customers who have had issues using power strips and battery backup devices.
Have you installed the latest OS updates as well as updated the USB controller drivers on your computer? Have you tried connecting your external hard drive’s USB cable into a different USB port on your computer? When connected to a different port, do you have the same problem? Have you tried a different USB cable? Are you experiencing any other problems with USB devices on your computer? Does your external hard drive have the same problems if you try it on a different computer?