imagecolortransparent & IE

Hi, I have been working to create a program that takes a user-uploaded background image, a little alpha blending, some data, and a pinch of fairy dust, and outputs a nice image. I have had trouble with the image displaying properly in Internet Explorer. An example: http://ffxi.nerdlife.net/ffxi.php?id=1 If you open it in any non-IE browser, it looks fine, but if you open it in IE, the gray background is not made transparent. My question is, how can I fix this, and if I can't, is there any alternative for making a transparent background. Here's my code snipplet:

       	$color = ImageColorAt($im, 1, 1);

imagecolortransparent($im, $color); Also, I output the file as a png file, but I don't care what it is output as (although my server for some reason doesn't recognize ImageGif...): header("Content-Type: image/png"); Imagepng($im); Any advice? Thanks, Brian