I've seen some identical problems but no solutions. So I decide to restart the problem.
I've got an Sony Vaio VGN-SR19VN and the sound does make his way out from speaker AND (&) from the HeadPhones
No, it's not a internal hardware problem because it works simply fine in W. Vista. I even did'nt know that this was a OS function but apparently is. I've got Ubuntu 8.10 and up to date.
So... anyone wants to share a solution? Because it's really annoying not to listen music in work...