desktop-effects doesn't work with fglrx/xgl

Binary package hint: desktop-effects

I am using Fiesty and Xgl as X-server on :0 - Beryl is running without any problems.
I'm running on a Samsung S60 Laptop with an ATI X1600 graphics adapter.
Whenever I try to activate desktop-effects the window decoration goes, it does something for a few seconds and then switches back to metacity, saying that desktop-effects could not be activated. Running desktop-effects in a terminal gives

atreju@lakshi:~$ desktop-effects
nvidia hardware not available
gtk-window-decorator: Could not acquire decoration manager selection on screen 0 display ":0.0"
/usr/bin/compiz.real: GLX_EXT_texture_from_pixmap is missing
/usr/bin/compiz.real: Failed to manage screen: 0
/usr/bin/compiz.real: No manageable screens found on display :0.0
Window manager warning: "" found in configuration database is not a valid value for keybinding "toggle_shaded"
atreju@lakshi:~$ Window manager warning: Fatal IO error 11 (Resource temporarily unavailable) on display ':0.0'.