Hyper V Backup Failure

hi,

we running media server on Windows 2008 Standard 64 bit Server and taking hyper v backup using symantec back up exe 2010 R3 with latest hotfix.

suddenly getting below error, could any one help on this.?

Backup
V-79-57344-65233 - AOFO: Initialization failure on: "VRTSRV::\\INMAA3BMS0013\Hyper-V?Virtual?Machine\INMAA3BMS0003". Advanced Open File Option used: Microsoft Volume Shadow Copy Service (VSS).

Snapshot provider error (0xE000FED1): A failure occurred querying the Writer status.

Check the Windows Event Viewer for details.

Writer Name: Microsoft Hyper-V, Writer ID: {66841CD4-6DED-4F4B-8F17-FD23F8DDC3DE}, Last error: The VSS Writer failed, but the operation can be retried (0x800423f3), State: Failed during prepare snapshot operation (8).

Regards

Ramesh TP