On Sun, 2008-06-01 at 16:14 -0300, pcpa@(protected):
>  GLX should still work correctly. Basically you only miss the
> Composite extension, that makes all windows contents a texture.
>
>  Since it still fails when using depth 24 by default, it is
> probably a problem that I am not aware of... You can try to
> run xwininfo and click on it's windows. If it is using a different
> depth than the root window, you probably will also want to change
> the default depth in xorg.conf to that depth, as basically all
> drivers will not accellerate windows with different depths, and
> may fallback to software accel to all windows.
>
> Paulo
xwininfo: Window id: 0x3a00163 "PyRAF Parameter Editor: tv.display"

Absolute upper-left X: 53
Absolute upper-left Y: 75
Relative upper-left X: 3
Relative upper-left Y: 25
Width: 770
Height: 689
Depth: 24
Visual Class: TrueColor
Border width: 0
Class: InputOutput
Colormap: 0x20 (installed)
Bit Gravity State: NorthWestGravity
Window Gravity State: NorthWestGravity
Backing Store State: NotUseful
Save Under State: no
Map State: IsViewable
Override Redirect State: no
Corners: +53+75 -457+75 -457-260 +53-260
-geometry 770x689+50+50

The xorg.conf file contains:
# File generated by XFdrake (rev 234840)


Section "Extensions"
  Option "Composite" "Disable"
EndSection

I had to insert "Disable".

-- Bjarne