tfs build server bluescreen

Our tfs build server has bluescreen issue for about 5 days since 8/11/2014.

Everyday morning, I come to office and I find build server has restarted accidently and following event message popup. Say there is a bluescreen issue occurred.

Seems the issue always occur at night. Because during day time, I haven't seen any bluescreen issue and message on build server

TFS: TFS 2012 RTM
Build server: windows 2008R2 with build tools installed, such as VSTS 2012 and vsts 2012 update 3
Build server is a hyper-v 2008R2 VM:

Problem signature:
  Problem Event Name:                      BlueScreen
  OS Version:                                       6.1.7601.2.1.0.274.10
  Locale ID:                                          1033

Additional information about the problem:
  BCCode:                                            50
  BCP1:                                                 FFFFFA7FFFFFFFEA
  BCP2:                                                 0000000000000000
  BCP3:                                                 FFFFF800016CC3FB
  BCP4:                                                 0000000000000007
  OS Version:                                       6_1_7601
  Service Pack:                                     1_0
  Product:                                            274_3

Files that help describe the problem:
  C:\Windows\Minidump\081514-1848015-01.dmp
  C:\Users\rttfsbuild\AppData\Local\Temp\WER-31758078-0.sysdata.xml

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Event log:

Event filter with query "SELECT * FROM __InstanceModificationEvent WITHIN 60 WHERE TargetInstance ISA "Win32_Processor" AND TargetInstance.LoadPercentage > 99" could not be reactivated in namespace "//./root/CIMV2" because of error 0x80041003. Events cannot be delivered through this filter until the problem is corrected.

We have run "Debug Diagnostics Tool 2" to dump file: "081514-1848015-01.dmp" . report is following:

WER-31758078-0.sysdata.xml doesn't have any helpful info too.:

After analysis the dump file, we have no idea how to fix it.

Search on google, there is no better reference too. Because the issue is critical for team. we decide to reboot Host server on 8/15/2014.

And till now (8/18/2014) we have seen the "blue screen" issue again.