fx5200 cards don't play nice with nouveau. You could try this as root:
echo 'options nouveau noaccel=1' > /etc/modprobe.d/nouveau.conf
and reboot. This disables acceleration for nouveau.
But, I don't think that would help much with KDE as it would need graphics acceleration. You will likely need the proprietary nvidia-legacy driver (173).
I could only see a SlackBuild for this for 13.37. Anyone see one for 14.0?