themistral

I got the same problem using PIE.htc from http://css3pie.com. The #content background and the h2 rounded corners on a gray background showed in Firefox but the h2 backgrounds didn't show in IE7.
 
I used your code in a test page (with my background-image) and cured IE7 with a z-index and position:-

#content { float:left; margin:0; padding:0 5px; width:960px; background:url(/images/template/main-background.jpg); z-index: -1; position: relative; }
 
I assume that border-radius.htc and PIE.htc work in the same way and I hope the z-index and position work for you.
 
 
A note in CSS3 PIE says this (although it might not be relevant but item 2. make the ancestor element position:relative and give it a z-index. is what I did ):-
Problems with z-index (disappearing backgrounds)
 
First, a little background on how PIE renders CSS3 decorations: a single <css3-container/> element is created which holds all the VML objects. This container element is inserted as a previous sibling to the target element, and absolutely positioned at the same coordinates. If the target element is position:absolute or position:relative, then the css3-container element is given the same z-index as the target element, and since it is a previous sibling in the DOM tree it gets displayed behind, with no possibility of any other element sneaking in between.
 
However, this does not work so well when the target element is position:static, because static elements do not participate in z-index stacking. The only way to make our position:absolute css3 element go behind it is to give it z-index:-1. Unfortunately, this has a bad side-effect: not only will the css3 element go behind the target element, it will also go behind the background of any ancestor element(s) which are themselves position:static. This leads to situations in which PIE creates the VML rendering correctly but it disappears behind a parent element's background.
 
The only way I know of to work around this is to either:
 
1. make the target element position:relative, or
2. make the ancestor element position:relative and give it a z-index.
 
Both of these workarounds can have potential unwanted side-effects in terms of child element positioning and z-index stacking. PIE could easily force one or the other itself, but:
 
1. One or the other may be more appropriate depending on the particular situation, so the CSS author needs to be able to control which one gets chosen.
2. Forcing position:relative outside of the CSS would put IE out of sync with other browsers, leading to confusing inconsistencies.
 
PIE therefore does neither, and it is up to the author to implement either workaround where necessary.