Error: VDI open failed due to requested abort... You can only perform a full backup of the master (4224908)

<ERROR error=11700>VDI open failed due to requested abort.</ERROR>
<ERROR error=12300>BACKUP DATABASE is terminating abnormally.
You can only perform a full backup of the master database. Use BACKUP DATABASE to back up the entire master database.

SQL Server log may include:
BACKUP DATABASE is terminating abnormally.. Possible failure reasons: Problems with the query, ResultSet property not set correctly, parameters
not set correctly, or connection not established correctly.

Differential backups cannot be used for the master database since, when restoring from a differential backup, the first step is to apply the full backup without recovery, which is not allowed for the master database.

For additional info, see Books Online orhttp://www.simple-talk.com/sql/backup-and-recovery/simple-talk-sql-server-backup-crib-sheet/