Possible Causes:

• The file the Backup Exec job log refers to belongs to an application which is open and in use when the backup is running.
• Advanced Open File Option is not enabled for the job.
• If the file mentioned in the job log is not present in the given location, Backup Exec is not able to backup that file and reports that as corrupt data encountered.
• Files are being locked by antivirus scan or drive defragmentation is running.

Try the solution mentioned on this technote (if not already attempted) - http://www.symantec.com/docs/TECH145966

(although the above technote refers to failed backup and you are getting exceptions, still worth try)