No system beep

[Chanchao]

My system beep isn't working, at least not audibly.

Sounds everywhere else work, so everything on the first tab of the
'Sound' Preferences panel works.  The second tab is the System Beep tab,
and this beep isn't played even though I have it enabled.  

When I select to also flash the screen then it does flash the screen,
just no beep.

Thoughts, visions, meditations anyone? :)

Cheers,
Chanchao