I have just replaced my system with LM 13 LTS Cinnamon 64bit. Everything was working (except that I can't disable my laptop's touchpad using the function keys, working on LM 14). Audio when playing movie is heard in my external speaker, as well as playing youtube on firefox.
But after updating LM, playing a movie on VLC and other media players, no sound is produced on external speaker. If jack is removed, a sound can be heard on internal speaker on laptop but not working on external speakers. Same with playing youtube on firefox. Sound can only be heard via laptop's internal speaker but when jack is inserted for external speakers, nothing... No sound.