I had been watching TV via Roku and I got up to check something on my iMac. For some reason, it was completely shut off and my wife and kids said they hadn't touched it. I restarted and found the ethernet to be non functioning, but I was still getting a wireless signal to all my devices. I restarted everything, pulled and reinserted all the cables (about the same as looking under the hood of your car when it breaks down and you have no idea why). Still nothing. I am being told a network cable is not connected, when it is. Could the ethernet (network?) card have gone bad? Thanks for any information or advice you can give.