For Blackdove 2.0 we converted from username to a combination of email and Facebook login. Usernames were a real problem for users in 1.0 and so we converted to email and FB to reduce the number of username requests.
For users needing to convert their accounts, please follow the following quick steps to get back online;
1. Create a new user account with either email or Facebook login (FB login recommended)
2. Send an email to email@example.com with your new email/FB username and your old username.
3. Give us a day and we will pull the accounts together and get you back up and running.