I have a single stand alone Hyper-V Box (Server 2008 R2 Enterprise) at a remote office that has two VMs. Both are Server 2008 R2 VMs.
Each night my backup software does a VSS Snapshot of the Hyper-V Host. During this process only one of the VMs virtual NIC goes offline.
Get an Event ID 10: The miniport 'Microsoft Virtual Machine Bus Network Adapter #2' disconnected.
Followed 10 minutes later by a Even ID 9:
The miniport 'Microsoft Virtual Machine Bus Network Adapter #2' connected.
This issue is isolated to this one VM on this one Hyper-V host.