I installed Amarok recently and was very pleased with it until it started freezing. I had previously used Rhythmbox, which comes with the default install of Ubuntu, but it decided to disappear along with the music it was playing a bit too frequently for my liking and it wasn't particularly aesthetically pleasing. The biggest problem with Amarok was that when I opened it, it didn't load. The process started, along with a helper process and some python and ruby processes, which I assumed were from scripts I had been playing around with, but no GUI.
I guessed that Kubuntu users don't run into this problem so I considered installing Kubuntu. I ended up only installing KDE's core components and that seems to have done the trick because now Amarok runs as expected!
This fixed my installation of Amarok:
sudo apt-get install kde-core