The epic Diablo III role-playing game experienced several hiccups on launch day today as players reported numerous errors preventing gameplay. Not long after the midnight launch, some concerned players hit parent company Blizzard’s Battle.net support forums with concerns about “Error 3006,” perhaps the worst error seen so far.
The bug, which only affects the Demon Hunter class, supposedly occurs when one equips a Templar follower with a shield early in the game. Performing this action reportedly causes the game to disconnect the player immediately, and then follows up with a disastrous repetitive “Error 75” that continuously prevents the user from further log-in.
According to Blizzard community manager Takralus, “The current workaround is to not give the Templar any gear until after you accept him as your follower through the UI pop-up.” A hot-fix for the issue may come as soon as today, according to a Blizzard representative.

Source: CNET