The operating system retured an unusual error while backing up the file.It is because the file is incomplete and therefore should not be restored.
Event id :57481
An unusual error () was encountered while enumerating the contents of the directory: \\Server01\D$\Software\temp. It is possible that files or subdirectories have not been backed up.
This event is reported by Backup Exec when it receives an error condition from Windows when attempting to backup a file.
CHKDSK should be run on the disk that contains the corrupt files. After running CHKDSK, try running the backup job again.
Run the Ntbackup(win2003) or Windows server backup(win2008) for that file or directory and check if getting similar result.