Unable to login to spotify behind proxy

[cosmic28]

Behind the firewall I´m not able to login to spotify with my mac book 

- open Spotify Application 

- get Login Screen with Facebook Button 

- click opens Safari "Loggin into Facebook"

- After a few seconds the Tab is closed but I am not in Spotify 

This happens wehn I am behind a proxy 

in ~/Library/Application Support/Spotify/prefs

I added the proxy with the line 

network.proxy.addr="proxy.XXX-XXX.com:3128@http"

When I try to login manualy with my facebook mail I get an error that the service is temporarly not available? 

Hope you can help me!

BR 

Alexander