Thanks for all the replies, guys.
SOLUTION:
I finally got it working, but the suggested fixes didn't quit do it because they all implement AlphaImageLoader which just replicates the same problem IE8 is creating all on its own.
The solution I finally got to work was to use a script called DD_belatedPNG (
http://www.dillerdesign.com/experiment/DD_belatedPNG/ )which uses Microsoft VML to fix the pngs (and allows fixing on a per-element basis, which is what I wanted).
Then I had to use a <meta http-equiv="X-UA-Compatible" content="IE=EmulateIE7" > to force IE8 to emulate IE7 and thus trigger the script.
With that combination, my f'd up PNGs are finally looking as good as they should in IE8!
Thanks again for the comments.
-Phil