Blizzard may have to trigger delays of up to 40 seconds when users log in to Battle.net to play Diablo III at launch on or around May 15. Those that fail to log in will get an "error 37 message," which may confuse them but they should simply try to log in again.
"It's possible we'll need to adjust the rate at which we're logging people in to ensure a stable experience, and if we do you may see a delay when attempting to login," Blizzard warned customers. "Please be aware that a delay of up to 40 seconds is possible while the game attempts to connect you. If your connection doesn't succeed in 40 seconds, you'll be presented with an Error 37 message and asked to try again.
The company is recommending that future Diablo III players create their BattleTags in advance of the game's launch if they haven't already done so to avoid delays in playing. In other words they expect servers to be bum rushed on launch.
"We expect that on launch night both the game service and website will be under very heavy strain due to the immense number of people excited to be among the first playing Diablo 3. With that in mind, we highly recommend you create your BattleTag now, as it's required to play Diablo 3."
On "error 37" Blizzard says not to worry too much about it.
"If you see this error it does in fact mean that you should try again. We'll be working around the clock to keep you informed of any issues that are occurring through the in-game breaking news window, as well as the official forums."
Blizzard also said that Global Play won't available until after the PC exclusive launches in the United States (12.01 am PT on May 15).
"We'll provide an update once Global Play is enabled, and you'll then be able to change the region you connect to through the game's options," Blizzard said. "Please note that characters, items, and friends lists do not transfer across regions and players who use Global Play to connect outside of their home region will only be able to access the gold-based auction house."
The reason all of this is problematic is because the game requires players to be logged in in order to play even single player. When log in problems occur or servers go down, this effectively stops everyone from playing a game that requires a constant connection.