Was not expecting to hit this issue with IE-8 - Couldn't work out how to make sure my div is transparent.
Here is the CSS I found from the IE Team blog:
-moz-opacity:.50;
-ms-filter: "progid:DXImageTransform.Microsoft.Alpha(Opacity=50)";
filter: progid:DXImageTransform.Microsoft.Alpha(Opacity=50);
opacity:.50;