I'm glad you got it working for IE7. I took a look at the code you posted and tried to get it working for my machine (Windows 7 x64) and got a working example for IE8

.TestDiv
{
background-color:white;
padding:15px;
border: 1px solid #aaa;
overflow:hidden;
margin-bottom:15px;
-moz-border-radius: 4px;
-webkit-border-radius: 4px;
border-radius: 4px;
background: -webkit-gradient(linear, 0% 0%, 30% 0%, from(#EDE8EE), to(white));
background: -moz-linear-gradient(left, #EDE8EE, white); /* for firefox 3.6+ */
-pie-background: linear-gradient(left, #EDE8EE, white);
position:relative;
behavior: url(PIE/PIE_uncompressed.htc);
}

<div class="TestDiv" style="width:100px;">This is a test</div>

That worked like a charm. I would try and see if that works as I know it does, and then go from there.

Great, thanks, I will test that! However, the problem could be related to parent containers I suspect.
That box is nested within 5 other containers or so on my page. Although none of them has a z-index set.

Nico

Ah, yes, seems to work. I think the IE8 modus of IE9 that I'm using doesn't work properly. My colleague just tested with a "real" IE8 and it works fine!