Installing the Hyper-V RC0 update for Windows Server 2008 rendered my virtual machines unable to connect to the network.

I installed the hypervisor - Hyper-V RC0 build today.  After rebooting, my network configuration would not function.  I was unable to add an External network and bind it to the NIC successfully.

I'm running Windows Server 2008 RTM x64, and I had the beta (in-box) Hyper-V code running with virtual machines.  My physical machine has two onboard NICs; one was dedicated for the host, and the other was for the virtual machines.

So I removed the HyperV role, and rebooted the box.

The box hung like this.  I power cycled it, which restored service.  The configuration was "resumed" and the role was successfully removed, with an error.  Unfortunately, the Virtual Switches stayed in Network Connections.  I then reattempted install of the Hyper-V role.  This completed, but with an error: it wasn't able to set up the networking components.

Log Name:      Microsoft-Windows-Hyper-V-Network-Admin
Source:        Microsoft-Windows-Hyper-V-Network
Event ID:      14070
Level:         Error
User:          SYSTEM
Description:
Switch set up failed, name='6d861a9b-39ef-4d01-a181-e163e5a21908', external port='f6400f7a-0dea-4b1f-bf91-3a78b00092f5', internal port='30b4be1c-5c03-48a6-84ed-7f590a3ffae7', NIC='{506E5818-0E27-4E13-8835-DDC8B7393D36}', internal name='9e3e1874-09ab-423b-904e-75420369499f', internal friendly name='New Virtual Network', error=2147749889, mof code=0.
Event Xml:
  <System>
    <Provider Name="Microsoft-Windows-Hyper-V-Network" Guid="{0a18ff18-5362-4739-9671-78023d747b70}" />
    <EventID>14070</EventID>
    <Version>0</Version>
    <Level>2</Level>
    <Task>0</Task>
    <Opcode>0</Opcode>
    <Keywords>0x8000000000000000</Keywords>
    <EventRecordID>88</EventRecordID>
    <Correlation />
    <Execution ProcessID="1088" ThreadID="1196" />
    <Channel>Microsoft-Windows-Hyper-V-Network-Admin</Channel>
    <Security UserID="S-1-5-18" />
  </System>
  <UserData>
      <Switch>6d861a9b-39ef-4d01-a181-e163e5a21908</Switch>
      <ExternalPortName>f6400f7a-0dea-4b1f-bf91-3a78b00092f5</ExternalPortName>
      <InternalPortName>30b4be1c-5c03-48a6-84ed-7f590a3ffae7</InternalPortName>
      <NIC>{506E5818-0E27-4E13-8835-DDC8B7393D36}</NIC>
      <InternalName>9e3e1874-09ab-423b-904e-75420369499f</InternalName>
      <InternalFriendlyName>New Virtual Network</InternalFriendlyName>
      <Error>2147749889</Error>
      <MofCode>0</MofCode>
    </NvspSwitchSetupError>
  </UserData>
</Event>

I've posted to some MSDN blogs' comments... but I doubt I'll hear back.

So now, I have no Hyper-V machines running anymore, and I can't get rid of the Virtual Network Switches.  I have heard from some people that manually removing the entries in the registry for the NICs will cause everything to "blow up".  I'm unable to delete the Virtual Switches in Network Connections, or in Device Manager.

My physical box has production workloads on it, so I can't blast it away.  Since the "finish line is in sight," I was kind of hoping that these kinds of things wouldn't happen, especially since they shipped the beta I was running inbox with the RTM code.

I can't find any evidence of Hyper-V on Connect, so there doesn't appear to be a way to report this.

Advice:

I would suggest that you remove not only the machines, but also the virtual networks, AND the Hyper-V role, before applying the update for Hyper-V RC0.  Then reinstall the role to make sure things are cleanly in place.

Further reading:

http://support.microsoft.com/kb/949222/ and http://support.microsoft.com/kb/949219