IE7/8 background transparency issue

[JDrysdaleJr]

I have navigation links that use a class that makes the link 100px wide by 40px high; selected uses background color; the rest are transparent (transparent 1x1 image with 100% opacity, no background color) and show the background image underneath with some transparency. Opening a modal in IE7/8 causes all opacity to disappear. As if the .png image has 0% opacity. Works flawlessly in FF. I love Reveal! Thank you!