I am running Backup Exec 12.5 rev 2213. My Exchange backups stopped working all of a sudden, for no reason. The backup was failing on a Windows 2008 Server with Exchange 2007 SP1 update 8.
The error I was getting was this:
Completed status: Failed Final error: 0xe00084f4 - An unknown error has occurred. Final error category: System Errors For additional information regarding this error refer to link V-79-57344-34036
An unknown error occurred on device "HP 1". V-79-57344-34036 - An unknown error has occurred.
I tried creating a new job, backing up one item at a time and about 100 other things. Nothing worked including Symantec's escalated "support." Strange thing was my Information Store backups would still work, but none of my system state, C drive etc...
I mistakenly created a new job but didn't pick the media set I usually use for my exchange jobs. Viola, the backup worked.
I simply created a new media set and changed it in the backup job. Job runs perfectly again.