This problem has been widely reported, and I'm posting here to give it a bump (and to say that it's still out there). Running the latest version of Spotify on a MBP 10.8.2. Was working fine, then out of the blue, stopped working. I start the app, login, and the app freezes (I get the "not responding" message and have to Force Quit).
I had this problem a while back, and after a couple of clean reinstalls and logging into the website first, it worked fine. Now, nothing seems to work. I've tried:
Multiple clean reinstalls
Logging into client with both Facebook login and Spotify login
Logging into the website (with both FB and Sp login) first and then starting app
Turning off my Internet connection then starting the app
Nothing seems to work.
Web player works fine, iPhone and iPad work fine. Just the standalone client.