When using jQuery to dynamically insert elements into an SVG (or any nested G-element), the inserted elements (g, circle, rect, etc) are never shown. When inspecting in Firebug they are there, but grayed out. When looking in the Layout-tab in Firebug it says that the width and height are 0.
<svg>
<circle fill="gray" r=80 /> <!-- this one IS displayed -->
</svg>
<script>
$('svg').append('<circle fill="red" r=40 />');
</script>
The code above works fine when adjusting elements outside svg, fx inserting an HR-element into BODY.
Screenshot from Firebug, DOM-inspector:
Screenshot from Firebug, Layout-inspector: