this is related to the newes alpha version of kubuntu, so its most likely a distribution problem... anyway...

after the latest update, installing the nvidia driver removes xserver-xorg and all its components completely .. reinstalling the xserver removes the driver ...

any idea what causes the problem and how to solve it? or do i have to wait for a fix?

I think a better course of action would be to raise it as a bug at Ubuntu.

It's clearly not a KDE problem as such, and if nobody bothers to tell them there's a bug at this stage of development of the next release, it could end up staying there.

or wait a day and try again - these things tend to happen often in the alpha stages of each *buntu version, and really should be expected this early in the development cycle.

k thx.. wait and report... thats what i'll do...