Hyper-V V1:

http://technet.microsoft.com/en-us/library/dd430893(WS.10).aspx

Hyper-V R2:

975530            Stop error message on an Intel Xeon 5500 series processor-based computer that is running Windows Server 2008 R2 and that has the Hyper-V role installed: "0x00000101 - CLOCK_WATCHDOG_TIMEOUT"

http://support.microsoft.com/default.aspx?scid=kb;EN-US;975530

974672            Virtual machines stop responding (hang) during startup and the Vmms.exe process crashes on a Windows Server 2008 R2 computer that has the Hyper-V role installed

http://support.microsoft.com/default.aspx?scid=kb;EN-US;974672

975354            A Hyper-V update rollup package is available for a computer that is running Windows Server 2008 R2

http://support.microsoft.com/default.aspx?scid=kb;EN-US;975354

974598            You receive a "Stop 0x0000007E" error on the first restart after you enable Hyper-V on a Windows Server 2008 R2-based computer

http://support.microsoft.com/default.aspx?scid=kb;EN-US;974598

976246            When you remove a virtual hard disk from a virtual machine in System Center Virtual Machine Manager 2008 R2, the .vhd file on the Hyper-V server is deleted without warning

http://support.microsoft.com/default.aspx?scid=kb;EN-US;976246

974909            The network connection of a running Hyper-V virtual machine is lost under heavy outgoing network traffic on a Windows Server 2008 R2-based computer

http://support.microsoft.com/default.aspx?scid=kb;EN-US;974909

975688            A snapshot may become corrupted when the Volume Shadow Copy Service (VSS) snapshot providers take more than 10 seconds to create it on a computer that is running Windows 7 or Windows Server 2008 R2

http://support.microsoft.com/default.aspx?scid=kb;EN-US;975688

976639            The Virtual Machine Manager Service crashes when you add a virtual machine host that has more than 16 logical processors in VMM 2008 R2

http://support.microsoft.com/default.aspx?scid=kb;EN-US;976639

976640            How to troubleshoot the "Not Responding" host status in VMM 2008

http://support.microsoft.com/default.aspx?scid=kb;EN-US;976640

976724            The SUSE Linux Enterprise network configurations are lost after a Hyper-V Live Migration

http://support.microsoft.com/default.aspx?scid=kb;EN-US;976724

976924            You receive Windows Time Service event IDs 24, 29, and 38 on a virtualized domain controller that is running on a Windows Server 2008-based host server with Hyper-V

http://support.microsoft.com/default.aspx?scid=kb;EN-US;976924

977509            A pass-through disk that is assigned to a virtual machine is not migrated when you upgrade to Windows Server 2008 R2

http://support.microsoft.com/default.aspx?scid=kb;EN-US;977509

977517            A computer that is running VMware cannot create a TCP connection to a NFS server that is running Windows Server 2008 R2

http://support.microsoft.com/default.aspx?scid=kb;EN-US;977517

972045            Slow system response together with many other performance issues occur on a virtualization server that is running Windows Server 2008 and that has the Hyper-V role installed

http://support.microsoft.com/default.aspx?scid=kb;EN-US;972045