You are on a multiplayer server running bukkit, and you have at least one mod installed (the minimap). We cannot help you unless you're playing vanilla. The mod might be the cause for all we know.
I'd advise pressing "force update" under "options" in the launcher. It'll remove your mods, but if it's still there then it is a minecraft bug and not from your minimap or any other mods you may be running.
I'd advise pressing "force update" under "options" in the launcher. It'll remove your mods, but if it's still there then it is a minecraft bug and not from your minimap or any other mods you may be running.