I recently installed Linux Mind Debian Edition (LMDE), and everything worked perfect, until I wanted to watch a video tutorial. There was no sound, though opening an mp3 file from the browser worked. So I googled a bit, found some hints and one solution:
I checked the files ~/.pulse/*-default-sink and ~/.pulse/*-default-source. The entries were different. One said alsa_output.pci-0000_01_00.1.hdmi-stereo.monitor and the other only alsa_output.pci-0000_01_00.1.hdmi-stereo After compliting the missing .monitor and forcing alsa to reload the configuration
sudo /sbin/alsa force-reload
the sound worked.