It is exactly what it says. The player got disconnected because mojang's authentication servers were offline at the time.
It only happens on our Server, I can enter any premium Server, except mine. If I do a restart, I can join again. This is happening every 30 Minutes or so.
online-mode: true? Edit: Saw post. Probably a plugin trying to store a player with a depreciated method.
It's probably Essentials: 2012-10-28 20:04:55 [WARNING] Essentials userMap not initialized 2012-10-28 20:04:55 [SEVERE] java.lang.NullPointerException 2012-10-28 20:04:55 [SEVERE] java.lang.NullPointerException Generating a new properties file...too many open files...what the hell is going on.. CraftBukkit #2415 EDIT by Moderator: merged posts, please use the edit button instead of double posting.
You are using a dev build, so things don't always work the way they are supposed to. This is especially true if you are using plugins that are not up to date.