Re: Floating point exception with 260.19.21.run version
I had the same issue.
KDE 4.5/4.6RC does not run on driver > 256.53 when using a too old kernel (or xorg...don't know which component is responsible).
However KDE > 4.4 run fines with a 2.6.35+ kernel and 1.9 xorg-server ; such a configuration is provided by openSUSE Factory (I'm running milestone 5 with KDE 4.6 beta and 2.6.37rc kernel and xorg 1.9.x), but it can be unstable.
You may ask tumbleweed to ship a newer kernel/xorg server (or wait 2 extra month before opensuse 11.4 ship); with current configuration, openSUSE 11.3 won't be able to run KDE 4.5 with nvidia drivers.
Notice that Gnome 3 has performance issue on xorg server 1.8 with nvidia drivers, solved with 1.9 xorg server.