OpenGL rendering problem

Hello,
I use Debian testing (lenny) on an i386 laptop. I use the commercial finite
element package ABAQUS and when I lauch its graphical environment ABAQUS/CAE,
I get the warning

eftaxiop@filippos:~$ /opt/abaqus/Commands/abaqus cae
ABAQUS License Manager checked out the following license(s):
"cae" version 6.5 from 147.102.246.1
<9 out of 10 licenses remain available>.
X Error: code 155 major 143 minor 5: GLXBadContext.

Warning: Your system needs to be reconfigured to allow OpenGL
rendering to a pixmap or PBuffer; otherwise, you will not be
able to print or use the probe function in ABAQUS/Viewer.

The programme is launched, but the probe function doesn't work. The same
version of ABAQUS used to work perfectly in Debian sarge.

Attached is my xorg.conf file

Section "Files"
FontPath "/usr/share/fonts/X11/misc"
FontPath "/usr/X11R6/lib/X11/fonts/misc"
FontPath "/usr/share/fonts/X11/cyrillic"
FontPath "/usr/X11R6/lib/X11/fonts/cyrillic"
FontPath "/usr/share/fonts/X11/100dpi/:unscaled"
FontPath "/usr/X11R6/lib/X11/fonts/100dpi/:unscaled"
FontPath "/usr/share/fonts/X11/75dpi/:unscaled"
FontPath "/usr/X11R6/lib/X11/fonts/75dpi/:unscaled"
FontPath "/usr/share/fonts/X11/Type1"
FontPath "/usr/X11R6/lib/X11/fonts/Type1"
FontPath "/usr/share/fonts/X11/100dpi"
FontPath "/usr/X11R6/lib/X11/fonts/100dpi"
FontPath "/usr/share/fonts/X11/75dpi"
FontPath "/usr/X11R6/lib/X11/fonts/75dpi"
# path to defoma fonts
FontPath "/var/lib/defoma/x-ttcidfont-conf.d/dirs/TrueType"
EndSection

Section "Module"
Load "i2c"
Load "bitmap"
Load "ddc"
Load "dri"
Load "extmod"
Load "freetype"
Load "glx"
Load "int10"
Load "vbe"
EndSection

Section "InputDevice"
Identifier "Generic Keyboard"
Driver "kbd"
Option "CoreKeyboard"
Option "XkbRules" "xorg"
Option "XkbModel" "pc105"
Option "XkbLayout" "us,gr"
Option "XkbOptions" "grp:alt_shift_toggle"
EndSection

Section "InputDevice"
Identifier "Configured Mouse"
Driver "mouse"
Option "CorePointer"
Option "Device" "/dev/input/mice"
Option "Protocol" "ImPS/2"
Option "Emulate3Buttons" "true"
EndSection

Section "InputDevice"
Identifier "Synaptics Touchpad"
Driver "synaptics"
Option "SendCoreEvents" "true"
Option "Device" "/dev/psaux"
Option "Protocol" "auto-dev"
Option "MinSpeed" "0.10"
Option "MaxSpeed" "1.00"
Option "AccelFactor" "1.0"
Option "HorizScrollDelta" "0"
EndSection

Section "Device"
Identifier "ATI Technologies Inc Radeon R250 [Mobility FireGL 9000]"
Driver "ati"
BusID "PCI:1:0:0"
EndSection

Section "Monitor"
Identifier "Γενική Οθόνη"
Option "DPMS"
EndSection

Section "Screen"
Identifier "Default Screen"
Device "ATI Technologies Inc Radeon R250 [Mobility FireGL 9000]"
Monitor "Γενική Οθόνη"
DefaultDepth 24
SubSection "Display"
Depth 1
Modes "1400x1050"
EndSubSection
SubSection "Display"
Depth 4
Modes "1400x1050"
EndSubSection
SubSection "Display"
Depth 8
Modes "1400x1050"
EndSubSection
SubSection "Display"
Depth 15
Modes "1400x1050"
EndSubSection
SubSection "Display"
Depth 16
Modes "1400x1050"
EndSubSection
SubSection "Display"
Depth 24
Modes "1400x1050"
EndSubSection
EndSection

Section "ServerLayout"
Identifier "Default Layout"
Screen "Default Screen"
InputDevice "Generic Keyboard"
InputDevice "Configured Mouse"
InputDevice "Synaptics Touchpad"
EndSection

Section "DRI"
Mode 0666
EndSection