G4 400 high-pitched squeal

[Eugene]

Ok, Big Problem.  Please read all before replying.

I have an AGP G4 400 running Yellow Dog 3.0.1 completely updated through
yum.  I absolutely love it, except....

When I log in, the desktop loads and right when the "volume control" icon
appears on the panel, a high-pitched squeal emits from my speakers.  If I
disable the "volume control" icon, the squeal starts whenever I start a
program (such as xmms) that accesses the sound card.  If I unplug the
speakers, the sound emits from the built in speaker at the front of the
tower.

I've searched all through the TerraSoft site for answers.  There is a thread
about powerbooks, something about CRT monitors and horizontal sync
frequencies, something about daughterboards, and I've tried ever fix they
suggest.  I've adjusted the monitor settings in every way you could possibly
imagine.  Still squealing.

Of course, if I boot into OS X or 9.2.2, I get no squeal at all.

Now the strange part:

Taking some of the info from the list, I opened the G4 400 and located the
daughterboard.  It's right below the processor.  While the computer was on,
running linux, and squealing, I pushed softly on the daughterboard.  The
squeal vibrated or modulated every time I pushed.  I pushed on different
parts of the board and got different reactions.  Then I pushed on the little
raised square named R63.  Instantly, I received several A.M. Radio stations
at once through my speakers!

Why, Why, Why?!  And how do I make it stop?!

Thank you in advance,

Eugene