error_37

As is stated within the "Error 37" sticky at the top of this forum:

http://us.battle.net/d3/en/forum/topic/371133225

For those experiencing the error message "Error 37", please try to login again at a future point in time. We are currently limiting the amount of testers that can login to the beta test and this error indicates that the servers have reached capacity.

Should any additional information become available, the aforementioned sticky will be updated.