Here are the error messages I get while trying to login with my spotify.com username and password:

18:32:35.241 I [offline_authorizer.cpp:297] Unable to login offline: no such user

18:32:35.242 I [ap:1752] Connecting to AP ap.spotify.com:4070

18:32:35.386 I [ap:1226] Connected to AP: 194.14.177.19:4070

18:32:35.888 E [ap:3953] Connection error: 409

(next trying email address instead of username)
18:33:31.572 I [offline_authorizer.cpp:297] Unable to login offline: no such user

18:33:31.573 I [ap:1752] Connecting to AP ap.spotify.com:4070

18:33:32.071 I [ap:1226] Connected to AP: 194.14.177.18:4070

18:33:33.948 E [ap:3953] Connection error: 410