The VSSADMIN command can be used to determine which VSS writer is causing your problem.
This is one of the Backup Exec errors that can be caused by a variety of conditions. NET Framework will vary depending on the operating system used. NET Framework and removing the framework can cause those applications to break.
You should therefore make a full system backup before attempting a registry modification.
After backing up the system, open the Registry Editor and navigate through the registry tree to HKEY_CLASSES_ROOT\Type Lib.
Again, restart the services after making any changes.
This is one of the Backup Exec errors that can be somewhat difficult to troubleshoot, as it corresponds to a read or write failure with the backup media.
Oftentimes, you can force a service to start by right-clicking on it and choosing the Start command from the shortcut menu.
After making any changes, it is a good idea to reboot the server.
You should also launch the Backup Exec Console and click on Tools | Backup Exec Services | Service Credentials | Change Service Account Information to ensure Backup Exec is configured to use an account that has been granted Domain Admin permissions (the actual location of this option may vary from one version of Backup Exec to the next).
However, VSS writer errors are tied to applications or the operating system, rather than to Backup Exec.
If a reboot does not clear the error, you will have to troubleshoot the VSS writer itself (and the underlying application) rather than Backup Exec.