Blizzard has corrected an issue with Diablo III’s servers in the wake of the first client patch’s release today.
The authentication issue was flagged by the Blizzard customer service Twitter as well as on the forum; both have since confirmed the servers are back online, but noted that high demand is choking log-ins.
“We’re aware that many players are receiving Error 37 when logging into the game. Please note that this error indicates that all servers are full, and that we’re currently receiving a high volume of login traffic. We’re working to reduce the frequency at which players are prompted with this error message and ensure that everyone can successfully log in to the game and play.”
Despite the reassurance, the European servers are currently offline.
It’s unclear whether the issue was related to today’s release of the very first full patch for the game.