As most of you know, I've made a windowblind called Copper Carbon Fibre, and I've used the layer feature extensively throughout it. Once I published it, I got a couple comments that the top part of the start menu would not show up in 64bit Vista. I was really suprised by that, because it worked fine in 32bit Vista.
Well, I figured out what was causing the issue and thought I'd post it here for others to see.
The base layer cannot be completely transparent. You must have something in the image. Pretty simple, huh? It took me a week to figure that out. 
Thank you, lgspence and ddraney for pointing out the bug to me! I'd have never know otherwise!