A game-breaking bug in Diablo III is already causing serious problems for the game's most hardcore fans. Players in a very specific set of circumstances have triggered "Error 3006", which kicks players off the Diablo III servers, and won't let them back on, according to Eurogamer.
According to reports, the bugs occurs when players attempt to equip the Templar NPC, who players meet early in the game, with a shield. Though unconfirmed, it's possible the problem may be restricted to those playing with the Demon Hunter class.
Blizzard has acknowledged the problem and is currently looking for a solution. In the meantime, it would probably be wise for players to avoid trading with their Templars until the bug has been resolved.