My PPC64 G5 machine is affected. Downgrading xserver-xorg-core from 2:1.5.1-1ubuntu3 to 2:1.5.1-1ubuntu2 fixes this for me. If your cache is still populated, try with:
sudo dpkg -i /var/cache/apt/archives/xserver-xorg-core_2%3a1.5.1-1ubuntu2_powerpc.deb
and restart gdm (sudo /etc/init.d/gdm restart).
My PPC64 G5 machine is affected. Downgrading xserver-xorg-core from 2:1.5.1-1ubuntu3 to 2:1.5.1-1ubuntu2 fixes this for me. If your cache is still populated, try with:
sudo dpkg -i /var/cache/ apt/archives/ xserver- xorg-core_ 2%3a1.5. 1-1ubuntu2_ powerpc. deb
and restart gdm (sudo /etc/init.d/gdm restart).