There must be a certain amount of free disk space, memory (RAM), and processor (CPU) time available for any type of open file technology to initialize properly.  In cases where AOFO fails to initialize when the Symantec VSP Provider is selected, the following can help with the diagnosis of the issue:

1. Confirm whether or not it is actually necessary to use AOFO for the backup.  Backup Exec Database Agents such as Exchange, Lotus Domino, SQL, and Oracle do not require AOFO to be selected in the backup job properties to be able to successfully back these resources up.

2. Make sure no other third party open file technology applications (Doubletake, HP Business Copy, St. Bernard's Open Transaction Manager, etc...) are attempting to snap the volume at the same time a backup runs.

3. Run a disk defrag and the Windows Error Checking each machine's hard disks at a time when AOFO is not attempting to initialize.  

4. Use a utility such as Process Monitor to find out if any there are any memory or CPU Bottlenecks.  

Sysinternals Process Utilities
http://technet.microsoft.com/en-us/sysinternals/cb56073f-62a3-4ed8-9dd6-40c84cb9e2f5.aspx

5. Modify the AOFO settings to use the alternate Microsoft Volume Shadow Copy Service as the snapshot provider if the Open file configuration is set to automatically set open file technology per the following steps:

a. From the Backup Exec console, Navigate to Tools  > Options > Advanced Open file.

b. Under "Open file configuration" change the "Automatically select open file technology" to "Microsoft Volume Shadow Copy Service".  In the drop down for snapshot provider, select "System - Use Microsoft Software Shadow Copy Provider".

If the VSS Backups also fail to initialize, there is most likely an issue with defective or malfunctioning hardware.  Contact the manufacturer of the hardware to have diagnostics run on the equipment.  If VSS Backups are successful, then this backup type can be used as an alternate method until it can be determined why the VSP Backups are failing to initialize or complete.

Please note:  In Windows 2000 there is no VSS Provider to be called when backups with AOFO are used.  In this case separate the Windows 2000 Server Backups using AOFO in a separate job from the Windows 2003 server backups with AOFO.  Set the Open file technology for the Windows 2000 servers to use VSP to snap and process the volumes.

For more detailed AOFO Troubleshooting Information, review the following document:

Why backups can fail with a "V-79-57344-34110 - AOFO: Initialization failure" when the Advanced Open File Option (AOFO) is selected in the Backup Job Properties 
www.symantec.com/docs/TECH71225