I unistalled something through Synaptic that messed with the sound of all my media.
The symptons are the following:
Any mp3 player does not play any mp3 media. It loads my music, but when I press "play" it freezes.
When I load any video in any videoplayer, it loads and start playing, but without sound. When I try to advance the movie a little bit, it freezes too.
I really messed it up this time.
Oh, any sound through the browsers, like Flash videos are okay. The sound of games are okay too.