Many Diablo 3 players, particularly those on the European servers, are receiving "Error 37" and "Error 3006" when logging into the game. It's just one of the few problems that have plagued Diablo 3 since it's launch earlier this month and a major problem players have with the always-online requirement of Blizzard's new game.
So this error is really nothing players are doing wrong, but rather an effect due to Blizzard's poor servers.
"We're working to reduce the frequency at which players are prompted with this error message and ensure that everyone can log in and play as quickly as possible," Takralus confirmed on the European forums.
In the meantime, players will have to continue to put up with login delays due to high traffic. Sorry Athene, you may have to attempt to break all Diablo 3 Inferno boss records once Blizzard has solved the problem.