Can't join ANY multiplayer servers because I am "already logged into a server"

I was playing the MineZ game when another player walked up to me and threw some sort of orb at me. when it hit me, i was immediatly kicked from the server and i think i saw it say something like "resetting your ip shouldnt be that difficult" ever since then, whenever i try to join any multiplayer game, it says i cant join because i am already logged into a server. Please help!