After Removing and Readding of an Hyper-V Network Card - No RDP Session to this W2008 R2 Host possible

Hello , 

I removed and after this i readded an virtual Network Card from an W2008 R2 Hyper-V virtual Machine. 

After this RDP Connections from this VM to other Servers are working. But when i try to connect from an other machine to this VM over RDP i become the Error "The Computer cant connect to the Remote Computer" . 

The W2008 R2 Server Firewall is disabled. The Remote Desktop Service is enabled. 

Thanks for Help . 

Michael