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The console mode fraebuffer and acceleration under X are two different things. Maybe I'd add a method to remove acceleration from X. Edit /etc/X11/XF86Config-4 and comment out 'Load "glx"' line. 'comment out' meas to put # before the line so it looks this way
# Load "glx"
If that doesn't work, look for 'Section "Device"'. There should be something like Driver "nvidia" close (instead of nviadia you may have a different thing, depending on the video card). Replace it with Driver "vesa". You should be able to start X then.