I don't blame anyone for not believing me, but honestly I solved the
ground loop whine that came up all of a sudden in my van's audio
system. What finally cured it was grounding the RCA out shields on the
head unit to the head unit chassis.

 From some internet research, it seems that this whine might be due to
a faulty component in the head unit itself, but in any case I fixed it
by this simple method shown here on my blog:

http://shufti.wordpress.com/2011/04/17/car-audio-ground-loop-whine/

alistair