extension "XFree86-DRI" missing

[Micha Feigin <michf@math.tau.ac.il>]

I am running Xfree86 4.3 from the unofficial packages by Daniel Stone.
When running matlab, and displaying graphics I get the following
message:
Xlib:  extension "XFree86-DRI" missing on display ":0.0"
I am not sure what kind of images produce this, since its not completely
consistent for some reason, but it includes 2D and 3D images and contour
plots.
I do have xlibmesa4-dri installed, the ati drivers from gatos for and
ati rage mobility m1 and a kernel compiled with drm support (r128)
driver. I also have a Load "dri" line in XF86Config.

What does this message mean, and can I do something to fix the problem?
Should I replace Load dri with Load r128_dri ?

thanks