BTW, adding a "NoAccel" option to video device section in xorg.conf seems to be a viable workaround:
Section "Device" Identifier "Configured Video Device" Option "NoAccel" "on" EndSection -- To UNSUBSCRIBE, email to debian-x-requ...@lists.debian.org with a subject of "unsubscribe". Trouble? Contact listmas...@lists.debian.org