Volume Shadow Copy service entered the stopped state

I use Paragon Backup version 10.2 in Windows 7 premium 64 bit to backup to an external USB Hard Drive. Backup used to work fine but now the backups fail halfway through. I've traced the problem through the Event viewer to be caused by:
"Volume Shadow Copy service entered the stopped state"

How do I prevent the Volume Shadow Copy service from entering the stopped state during a backup?
Thanks.

P.S. The error message during Paragon's backup is
Backup [virtual] succeeded

Backup [committed] failed
VSS: Can't read volume data
Error code 0x 12016

When I switched Paragon to use its own hot processing instead of Window's the error message became:

"Backup [virtual] succeeded

Backup [committed] failed
VSS: Can't read volume data
Error source: Hard disk manager
Error code 0x 12016"

Here's an old article on the subject http://support.paragon-software.com/showthread.php?t=501

Thanks. I had read that which is why I had Windows check that partition (selecting both "fix file system errors" and "Scan for and attempt recovery of bad sectors").
Is there a separate disk utility available to check the hard drive better?

It's a new laptop and the hd should still be under warranty.

Thanks.

Your Antivirus could also be causing the problem.

How do you mean? I am using Avast free latest version.

Disconnect from the Internet, then turn off/disable Avast ... now see if you can use Paragon Back-up without a problem.