I've had similar problems in the past. Make sure that whatever DNS server you're using is accessible. Also, make sure that your virtual networks are set up properly. If they're not, you'll have this problem. Like you, I use a router VM in Hyper-V.
Sometimes, disabling/renabling the NIC works, but in any event, run through your Hyper-V network settings to make sure that default gateways, etc, are set up properly.
hi not yet ! only changing the power option to high performence caused the error to show up less than before !! i have some linux vm which for those i only have to restart them time to time... if not i lost acces to them !! how'bout u any progress ?