No 3D acceleration for Radeon X1250 (RS690)?

["Slim Joe" <slimjoe2k8@gmail.com>]

I'm using the onboard graphics of my Asus M2A-VM
motherboard, which is identified as a Radeon X1200
(RS690). XVideo works with the default open-source drivers,
although there's noticeable tearing in the video.

However, I cannot get hardware 3D acceleration to
work. I get the following console message when running
glxgears/info:

unknown chip id 0x791e, can't guess.
libGL warning: 3D driver returned no fbconfigs.
libGL error: InitDriver failed
libGL error: reverting to (slow) indirect rendering

I have the following X-related libraries installed (output
provided by filtering the output of dpkg through the filter
'drm|mesa|radeon'):

libdrm2 [2.3.1-2]
libgl1-mesa-dev [7.0.3-6]
libgl1-mesa-dri [7.0.3-6]
libgl1-mesa-glx [7.0.3-6]
libglu1-mesa [7.0.3-6]
libglu1-mesa-dev [7.0.3-6]
mesa-common-dev [7.0.3-6]
mesa-utils [7.0.3-6]
xserver-xorg-video-radeon [1:6.9.0-1+lenny4]
xserver-xorg-video-radeonhd [1.2.1-2]

Is this a configuration problem fixable by placing the
correct entry in xorg.conf? Or is this a known limitation
of the current radeon driver? Note that I'm running without
an xorg.conf at the moment.