When I install NVIDIA-346 I get 149 Packages to newly install. Included in the list are Gnome and Unity packages, eg

unity-control-center unity-control-center-signon unity-greeter unity-settings-daemon

This indicates gross errors in packaging for KDE 15.04. This problem has been reported in the Kubuntu Forum. I could not file a bug report on this issue, so I decided to report the problem here.

The packages for installing the NVIDIA drivers for KDE therefore need to be made for KDE and NOT Unity.

this is a Kubuntu packaging issue not a KDE one, there are no "Nvidia drivers for KDE" there are drivers for Linux. If you look at the .deb files there might be some sort of text file with the packager's name and email so you could try contacting them

as to why you can't post a Kubuntu bug, you need to ask them

suggestions:
- try a different ppa
- try a different version of the driver
- compile your own, actually pretty simple once you have the required libraries
- try the Nouveau driver

Moved to the Operating Specific -> Linux forum