Backup process failed with code 100161

Hi,

Latest version of CB installed on Windows 7 -64-bit machine. Backing up to a WD ShareServ Network Drive.

Setup Files and Folders backup, User Files (documents, mailbox files, etc.), Synchronized.

On the initial backup it fails after about a half an hour and after transferring about 5000 files - around 4.2 GB worth. It seems to fail after successfully copying all the .PST files, but fails to move onto the next folder.

Any ideas what could be causing this and how I could remedy the situation?

You help is very much appreciated! Thank you!!