I think I've found the issue... missing/invalid DOCTYPEs.
I inserted the following line at the beginning of my document, and the resetting of the ajax colors started working in IE8 (which I went ahead and installed after doing my security updates).
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 1.0 Transitional//EN">
Mark, you have "4.0" instead, but if you change it to anything starting with 1, I think it will work.