I have a Windows host system which is running an Ubuntu guest inside VirtualBox. While the Ubuntu guest is running, I hibernate the Windows host. Later, after the Windows host is resumed, I find that network connectivity is lost in the Ubuntu guest. The LAN network interface is present and shows as connected. However, no domain name can be resolved or pinged.
I found that this bug in VirtualBox is reported here. Disconnecting the network interface and connecting back did not work. But, turning off networking and turning it back on worked!
Tried with: Ubuntu 14.04, VirtualBox 4.3.20 and Windows 7 Professional 64-bit