Long story short, mainboard swap, AHCI activated.
Usually I am a Debian follower, the freeze of Squeeze however seems to have a bug and the installer refuses to install grub in the MBR with AHCI. As I am too old by now to have time to hack this and work around I thought I give Kubuntu a go again.
However, what worked in Debian seeems an impossible task in Kubuntu - setting up X to span over both screens.
Installing the proprietary nvidia driver was a walk in the park. Was also easy to setup twinview to have both screens activated (I got one screen per graphics card)
However as soon as I try to activate xinerama to fool X into believing the twinview is one big screen to span the desktop over both, X starts up, nvidia logo flickers and I crash back to tty0.
With xinerama disabled it starts up just nice.
Granted an Ubuntu forum would be a better place to ask, but I think dualscreen/dualcard isn´t exactly a topic for the 101 ubuntu user and the issue has cropped up before for one of you guys.
It shouldn´t really make a difference that I am running Kubuntu instead of Ubuntu, KDE/Gnome just span over whatever X reports back to them.
Any hints, gentle pushes into a direction or linkage thats beyond ubuntu-noob forum is greatly appreciated.
What´s working in MacOS and Windows for ages out of the box still seems to be a stepchild in Linux.