Hyper-V guest system caused NIC connectivity issue

I am doing a forensics investigation into an error that occurred on our Host Hyper-V Server. 

A Domain Controller running W2K8 w/ SP and using Hyper-V lost its network connectivity so that I could not access the DC via RDP (network connectivity was lost). The only method of gaining access to the DC was via KVM attached to the box.

This seemed to occur because of the virtual NIC used by Hyper-V Network Manager.  When I removed the Network Manager for the Hyper-V server, connectivity was restored (after a DNS refresh).

Before I build a new Net Mgr and deploy it on the DC (Host server), I'd like to understand what happened so as to prevent this issue from occurring again.  Any ideas?

Thanks, Jesse