I've been having problems getting Skype to work properly on Ubuntu 13.04. When Skype was running properly the other audio applications on the box wouldn't work. If I started Skype while other audio applications were running then I'd have to audio in Skype. Ubuntu uses the PulseAudio audio server for its audio services and so does Skype, so things should have been working. However, when I went into the Skype options panel PulseAudio wasn't listed as a possible audio device.