no volume display in XMMS

[Andrew Schulman <andrex@alumni.utexas.net>]

I'm just getting to know XMMS, and I like it a lot.  But I have one problem:  
the volume analyzer and all of the visualization windows all show zero.  That 
is, I get no volume display.  I want a volume display!

One reason that this might happen (I guess) is if I'm reading analog instead 
of digital audio.  But as far as I can tell, I'm reading digital.  Under 
Preferences | Audio I/O Plugins | AudioCD Reader | Output | Output mode, I 
have "Read Digital CD Audio" checked.

Can anyone suggest how to get my volume display working?  Thanks!
Andrew.