Minecraft crashes X11

Description:  Minecraft crashed my X server during regular gameplay.

Reproduction:  Unknown.

Reason for Private Security Level:  Seeing as the cause for this is unknown, it's possible that this could be used maliciously, e.g. a malicious server could use it to force-crash clients, a malicious player on a server could use it to force-crash people to gain an advantage, a malicious mapmaker could use this to force-crash users who play their maps.