Minecraft crashes when clicking "Play Demo"

[Kevin Lin]

Description: Ubuntu 12.04.3 LTS
Release: 12.04

Minecraft Launcher 1.2.2

 fatal error has been detected by the Java Runtime Environment:
Client> #
Client> # SIGSEGV (0xb) at pc=0x00007fa49f47aae8, pid=4120, tid=140345251714816
Client> #
Client> # JRE version: 6.0_27-b27
Client> # Java VM: OpenJDK 64-Bit Server VM (20.0-b12 mixed mode linux-amd64 compressed oops)
Client> # Derivative: IcedTea6 1.12.6
Client> # Distribution: Ubuntu 12.04 LTS, package 6b27-1.12.6-1ubuntu0.12.04.2
Client> # Problematic frame:
Client> # C [libX11.so.6+0x33ae8] XQueryExtension+0x28
Client> #

Supposed to play and launch Minecraft.
But crashes and fails to load. Then it restarts.