Came across this one today. A DOM element had CSS3 border-radius: and box-shadow: attributes applied to it. Worked perfectly in everything except good old Internet Explorer, specifically IE9.

Turns out the reason for my ugly looking border-radius: and box-shadow: effect (instead of my nice smooth, anti-aliased shadowed corners) was because a legacy filter: dropshadow(color=#e0e0e0, offx=0, offy=1); attribute had been applied to affect/hack the newer CSS3 text-shadow: attribute for IE8.

Turns out, as of IE9, most of the filter: attribute methods on MSDN are officially deprecated.

Simply removing this attribute and replacing it with the newer, CSS3 standards based, text-shadow: attribute corrected my hideous looking, black rounded corners/box shadow effect in IE9.

Not sure if anyone else is looking to solve this, but hope it helps in some way.