Laptop volume control screw-up

[Harry Wert]

All has been well with Ubuntu Feisty release until I apparently
inadvertently fouled up the laptop volume control - how I do not know.
In any event I still get the on-screen display depicting volume control
when I press the appropriate button; ie, "mute", "volume increase", or
"volume decrease". The downside is the sound is now unaffected. I can
still point to the panel which displays the volume symbol with the mouse
and everything is correctly controlled.  I have done the usual looking
for an "accidentally installed" mixer, but the only one I can find is
the one for Gnome - which is correct.  Can anyone suggest how I can
isolate this problem.  It's trivial but annoying!

Thanks in advance,

Harry