Plasmashell crashes every few minutes because of gfx driver

[JPT]

I've got problems with the nouveau driver. It makes Plasmashell crash every few minutes. Since I don't know what Plasmashell actually does, I don't know which Plasmashell task crashes. Probably it is related to signaling apt package updates.

nvidia-304 driver does not work at all (blank screen)

Hardware:
GeForce 7600 GT
AMD Athlon(tm) 64 Processor 3800+
Via Chipset
Asus A8V-VM SE

I already thoroughly tested hard-disk and memory, everything OK. If you can suggest a tool for CPU and GFX burn in test...

If I remember correctly, I experienced the problem with Kubuntu 14.04 LTS, too.
I was able to workaround by installing the the Nvidia driver. In 16.04 the Nvidia driver doesn't work either.

ProblemType: Bug
DistroRelease: Ubuntu 16.04
Package: xserver-xorg-video-nouveau 1:1.0.12-1build2
ProcVersionSignature: Ubuntu 4.4.0-57.78-generic 4.4.35
Uname: Linux 4.4.0-57-generic i686
ApportVersion: 2.20.1-0ubuntu2.4
Architecture: i386
CurrentDesktop: KDE
Date: Tue Jan 10 12:58:26 2017
InstallationDate: Installed on 2017-01-05 (4 days ago)
InstallationMedia: Kubuntu 16.04.1 LTS "Xenial Xerus" - Release i386 (20160719)
SourcePackage: xserver-xorg-video-nouveau
UpgradeStatus: No upgrade log present (probably fresh install)