Are you making use of AOFO? If this is a remote server, have you ensured that RAWS is correctly installed, that the service is running, and that the agent is working?

Try rebooting the server and tehn try backing it up. Incase if the issue persist try backing up using windows 2008 backup utility ..

please unselect the resource from the resource order and reselect it try a backup.

just another thing, in your job properties
in Advance open File please select the

Microsoft volume shadow copy service and in the drop down select the system- use microsoft software shadow copy provider and then run the job

Thanks, I have tried all suggestions and I found the following in the log file.
_________________________________________________________________________________
[3688] 07/06/09 16:36:34 brUtil::OpenActiveObject Error: 0xE0008488 Could not open the object
C:\Windows\SYSVOL\sysvol\<Domain Name>\Policies\{269E26E0-D245-4870-837E-B9D41FEE9A11}\
[3688] 07/06/09 16:36:34 Status FS_ACCESS_DENIED (0xE0008488) for Component SYSVOL Share in SHADOW::ReadComponent
[3688] 07/06/09 16:36:34 AD:Status FS_READING_OBJECT_FAILURE (0xE000FEDF) calling FS_ReadObj in
SystemState::ReadObj:262
[3688] 07/06/09 16:36:34 Informational: Closing Component 'SYSVOL Share'
[3688] 07/06/09 16:36:34 Informational: calling IVssBackupComponents::SetBackupSucceeded with status
'FS_READING_OBJECT_FAILURE (0xE000FEDF)' for Component 'C8530777-DC35-4DCC-9DD0-99D76AFE406A-98EA160B-D77E-48AF-BC01-
C63D7969EE19' in SHADOW::CloseComponent

refer the following document http://support.veritas.com/docs/287544.
let me know if the backup with the windows backup utiltiy was successful or not

Thanks, I done the following, it can backup now but the speed is slow. (Why?)
1. Backup with Windows Backup at DC
2. Reinstall 2008 SP2
3. Change logon account.

  Is the throughput slow for just the system state backup or compete backup . Throughtput for the system state backup is ideally slow then the other volumes which you backup .And Goint eh throughput issue is mostly environmental .

you can use the technote Document ID: 285756
http://support.veritas.com/docs/285756 in order to improve the performance i.e B2D B2T