virtualbox.org

Failed to open a session for the virtual machine Ubuntu1404.

Failed to open/create the internal network 'HostInterfaceNetworking-Realtek PCIe GBE Family Controller' (VERR_INTNET_FLT_IF_NOT_FOUND).

Failed to attach the network LUN (VERR_INTNET_FLT_IF_NOT_FOUND).

Result Code: E_FAIL (0x80004005)
component: Console
Interface: IConsole {8ab7c520-2442-4b66-8d74-4ff1e195d2b6}

Anyone know why?

A question about an Ubuntu guest does not belong in the "Windows Guests" forum. And in fact the guest is irrelevant anyway. I'll move this topic to "Windows Hosts".

In Control Panel | Network Connections on the host, open the properties for that NIC and make sure "VirtualBox Bridged Networking Driver" is present and ticked.

If it isn't present then you skipped it during VBox installation. On x64 Windows hosts you should use "Run as administrator" to run the installer. Also make sure that "Driver Signature Enforcement" (Win7-x64 and later) is not configured to silently reject non-MS drivers.