The 'Active Directory' returned 'A disk I/O error occurred.
' from a call to 'BackupTruncateLogs()' additional data '-'.
This error appeared on a Windows 2000 server that was performing a backup of the System State. The message was logged after the start of the System State backup, and before the end of the system state backup was logged.
Rebooting the server resolved the problem and the error message is not logged anymore during backups.