[Plugin: WP-Syntax] works in firefox 3, but not ie 6

Heh, you said IE6. WP-Syntax should work in IE6 by default, but custom WordPress themes can really do a number on it, and I cannot chase all the rendering problems and bugs that IE6 has. From here on out, WP-Syntax will no longer support IE6.

IMO, anyone writing or reading code should have upgraded to IE7+ or left IE altogether some time ago, so the market is too small to worry about anymore.