The measures that have been taken to keep the site robust against denial of service attacks have caused this unintended consequence.
In short, requests made to EM servers are routed through a network of other machines that exist to filter and offload malicious traffic. These same machines are used to process user logins, which causes different users to have login conflicts with each other.
Unfortunately, there's no easy way for us to avoid this problem while maintaining anti-DoS protection, so for now please send any moderator a PM requesting to be whitelisted if this happens to you.
In short, requests made to EM servers are routed through a network of other machines that exist to filter and offload malicious traffic. These same machines are used to process user logins, which causes different users to have login conflicts with each other.
Unfortunately, there's no easy way for us to avoid this problem while maintaining anti-DoS protection, so for now please send any moderator a PM requesting to be whitelisted if this happens to you.