Comment 31 for bug 1186800

I've told you exactly what the issue is:

"No, that is a bug in adobe's software renderer not being able to handle any none 24-depth framebuffers. It equally affects you if have a 30- or 36-bpp monitor. The correct workaround here is specifying DefaultDepth 24 or just complaining to adobe."

The active ingredient of your workaround is changing the framebuffer depth.