Are you connected to a home LAN, corporate network or an ISP using the
network card? The possible causes are.
1. Defective network cable.
2. Loose RJ45 port on network card(this happened with my on-board network
card and I had to install an add-on lan card)
3. Issue with the computer/network at other end. The error message will
appear even if the network cable is unplugged at the other end.
Software issues are less likely to cause this error.