When I say you need the snapshot, it means you need the snapshot... Like 10 people have joined and got denied because they were using an older version.
I joined and spawned in the void below the ground. I can't get out because I'm at y=-2310 and keep falling without taking any damage.
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If you're on the latest snapshot and your sign text has vanished, you're hallucinating. Well, okay, you're not hallucinating, but any text you put on signs which disappears when you come back to it later (or change to the snapshot) is still there, just invisible. Proven by updating to 1.2.5 after raging at the loss of my "Wall of signs" which is basically a wall of signs with random fruit names on it. Took quite a while :D
Oh, and don't go above Y=191. Nothing renders up there and you get stuck like you do when you attempt to walk through a world hole/chuck error unless you happen to be falling or riding a boat (interesting concept in the air) or minecart.