Yes, that helps. I must have missed it when you posted yesterday.
It's explicitly looking for libGL.so.1.2 in /usr/X11R6/lib, but the GLX driver installs nVidia's version into /usr/lib (which is where it should be; I don't know who compiled that version of KDE, but I think they were a bit ... strange, making it hardcode the path to the library like that). This may not work, but it's worth a shot. Try cd /usr/X11R6/lib and then (as root) ln -s /usr/lib/libGL.so libGL.so.1.2 && ln -s libGL.so.1.2 libGL.so.1 && ln -s libGL.so.1.2 libGL.so. Run /sbin/ldconfig after all that, and see if KDE starts up.
What these commands are doing is faking KDE into thinking there's a libGL.so.1.2 file in the directory it's looking for it, so that (hopefully) it finds it. But it's just a symlink to the real libGL (the nVidia one), so you still get hardware acceleration.