One of the backup files could not be created. Detailed Error: The request could not be performed because of an I/O device error. Error code: 0x8078002A.
This occurs if you have either an advanced format drive or a drive that is over 2tb. To fix this problem you can either copy all of the files off of the drive and reformat it using a utility from the manufacturer or install KB982018 from Microsoft. I recommend trying to install the update first since it takes a lot less time.
You could also try running a checkdsk on the drive. If the drive had been removed improperly from the computer windows may not backup the drive.
If you have a drive from Segate that is 3TB, try copying all the data to a safe location and then reformat the drive in windows using the GPT format.