I just recently installed Ubuntu 14.04 and now, after I ran VLC for the first time, the audio doesn't work anymore. Before, everything worked just fine, but as soon as I opened a mkv-Video in VLC, the audio for the whole system stopped working.
After that I removed VLC and any plugins that have been installed with it, rebooted, but nothing changed.
Neither my monitor speakers nor my headset is working anymore, so I think it might be a problem with pulseaudio.
Here is a screenshot of my sound settings. Also to mention, my monitor speakers are hooked up to my nvidia graphics card via HDMI. (Newest graphics drivers are installed).
I just noticed that YouTube videos also won't play anymore, neither video nor sound. It just freezes at the first frame, continues buffering but doesn't play.
I recently installed flashplayer, but removed it again because it was causing problems. So I'm using the native HTML5-Player of YouTube. I tried both Firefox and Chrome.