Server freezes after attempting to backup system state and C drive.

Hi all,

Would love to have some advise on this issue.
Background: Server OS 2008 r2 SP1 64bit
BE 2012 v14.0 rev 1798 (64-bit)

My backup jobs for system state and C drive will always complete backup with execptions.
Execption is VSS Snapshot warning. File %BeBootDrive%\bootmgr is not present on the snapshot

On wednessdays, the backup job will hang with the error E0008821
My server will freeze after which. I will be able to ping the server and move the mouse at the server but will be unable to do anything else.
I have to force restart my server. Once the server restarted, The job will attempt to continue but will fail with the error 80004005.

Please help.