[Derek Beaney]

I would try Restarting the Volume snapshot service. If that does not work for you. the next step would be:

1. Recreate the backup set.
2. On The options Screen, choose the option for Incremental \ Differential backups.
3. Below that choose the option for "full backup"

What this will do is instruct UltraBac to use its own driver to freeze the drive.