this did not work for me but you may have better luck.

"If you need to use an app that doesn't work well in xgl (eg some java apps have an empty window for me) you can use Xnest which is like the windowed xgl, only the other way around =)

Here's an example usage for LimeWire:

Xnest :1 & DISPLAY=":1" limewire"

quoted from http://gentoo-wiki.com/HOWTO_XGL/Tips_and_Tricks