Hyperv Server 2008 R2 bluescreen...probably CLOCK_WATCHDOG_TIMEOUT

ref: http://social.technet.microsoft.com/Forums/en/windowsserver2008r2virtualization/thread/116a0220-6082-47d7-9bcf-bdde87c3ddf7

See this KB article http://support.microsoft.com/kb/975530 for a hotfix for Intel Nehalem processors.