HELP Failed to Login: Invalid Session (try restarting your game)

I am wishing to start a server but when I try to login, the client says Failed to Login: Invalid Session (Try Restarting your Game). I have tried closing the client then opening it again and that doesnt work I've tried restarting the server that doesnt work. If any other information is needed just say so I should be able to find it. Any help would be greatly appreciated. Thanks!


P.S. on the console, it says ID:null then it has my username and ip then disconnects me. Also, I am trying to join using the host computer. I use to run a vanilla minecraft server and it worked fine but the bukkit server is not working.