-moz-win-borderless-glass for Mozilla (non-native) popups causes a black background that does not seem to be modifiable

[DAPOPOBEFASTONYOAZZ]

With some elements modified with userChrome.css, some elements can use Windows Aero styling by using -moz-win-borderless-glass. On Mozilla's new styling for popups (Downloads and tab preview popup for example,) when -moz-win-bordless-glass is applied, a Windows Aero border is applied (albeit very small,) but the background color of the popup is black and does not seem to be modifiable with the browser toolbox and the element cannot be made transparent to take advantage of Windows Aero styling.

Given that the border that is applied uses Windows Aero styling, these popups should be able to have a transparent background rather than black to take full advantage of Windows Aero. Is there a way to fix this? Pictures are attached, You'll need to zoom in and look very closely for the Aero border.

[K4sum1]

What's an easy way to replicate this? I'm going to have to bisect anyways for another bug so might as well tackle this too.

[DAPOPOBEFASTONYOAZZ]

I'll attach my userChrome.css file so you can import it and experience it firsthand.
UC Build 1.29.zip

Also attached is the settings for the r3dfox appearance that may interfere with this theme if left enabled.

Edit: I should also note that the chrome files are quite messy, so they may not be the most friendly to read. It's a work in progress still and I will eventually clean it up. My apologies in advance should you need to dig around and see if it's userChrome related or Firefox/r3dfox related.