Your xorg.conf file is missing some lines that I have in mine under feisty. In the Screen section there's a GLX option line:
Identifier "Default Screen"
Device "Generic Video Card"
Monitor "Generic Monitor"
Option "AddARGBGLXVisuals" "True"
And at the end of the file I enable Composite:
Option "Composite" "Enable"
Also, in the NVIDIA configuration utility, ensure that in the OpenGL Settings section, the Image Settings are set to "High Quality."
Hopefully that will get you up and running. I've made other changes to my xorg.conf file, but none related to Beryl.