If you upgrade Spotify for Linux to 0.8.8.x version and you have some network connection problems (for example you're behind a company firewall and need to set a proxy...) the application will crash/hang without letting you doing anything (neither setting Proxy informations)
This is caused by a deadlock in the GUI and you can view the complete debugging informations here http://pastebin.com/zcKgXEqz
To fix this, you just need to open this file ~/.config/spotify/prefs and add these two lines:
network.proxy.addr="123.123.123.123:1234@https" network.proxy.mode=2
of course substituting 123.123.123.123:1234 with your proxyip:proxyport.