I am trying to set up a private blockchain for the first time with a Geth client. After initializing my custom genesis json file, running the networkid in the console and setting up a couple of accounts to start off with I then attempt to begin mining via the miner.start() command to get a few ether to test in the private chain. It looks like it's about to begin mining but then I get kicked out of the console and my screen looks like the attached screen shot. I've tried multiple times and in different directories with no luck. Can anyone explain why I am experiencing this issue? Thanks.