I was monitoring the mopidy process with "top" and I could see it crash after 30 seconds or so. Audio would be interrupted as well.
I was able to reinstall and get it working again but I noticed something.
When I flashed the SD card with PiMB 0.6.0 on Raspbian, I was able to install it but the web UI wasn't coming up at all even with all the necessary config in place.
Because I've had the same issue with other images, I decided to flash it again on Windows using a program called Image Writer and this time around it worked just fine.
I will try to install apache2 and that web interface again and see if I can get it to work again. I'll update this thread once I get around to do it.