hello guys my mplayer does not output sound!

No matter what file i play be it a avi, or the flv. when i try to toggle the sound buttons on top of the n800 it just doesnt respond.

When i try to play an avi file via xterm it says could not open/initialize audio device- no sound

I have uninstalled and reinstalled and also did a total os reinstall still acts the same.

Please some one help