My Book for Mac Back Up with Time Machine

I just got my My Book in the mail today and I was setting up, following the instructions. I wanted to use this backup my macbook that is running Mac OS X Version 10.7.5. It is all up to date on software updates. Whenever I try to start the back up, it will transfer about 4-5GB and then say the hard drive was ejected unexpectedly, and then the back up stops. It has done this about 5 times now. I have turned off sleep mode and screen savers to prevent the computer from shutting down. I made sure that the hard drive and the computer are using the same format in Disk Utility. Any help would be nice so I can get a safe back up of my laptop.

Thanks in advance. 

Hi,

Are you connecting the drive directly to the wall outlet or a power protector? If is on a power protector, try connecting the unti directly to a wall outlet and make sure to test the unit on a different USB port. 

Also, will be good to try transferring some files directly to the drive like drag and drop or copy and past to see if is a drive issue.