Norton 360 Backup Failure

I get this 100% of the time trying to backup about 1.3TB to a Drobo NAS. HELP!

I have tried several times to run a backup, which results in failure each time and a restart of my system to try it again.

 

I am trying to do an initial backup using 360 v5 to a network storage device with 1.5TB space (1TB free), Windows XP SP2

 

The backup process seems to run fine, but each time it gets to a point of finishing some file (not always the same file) at 99%, says it is processing, but never finishes. I then stop the backup and later try to restart it, but then have to restart my PC because Norton reports a current backup process running. There are no other apparent issues with other aspects of 360.