Kubuntu 8.10, Nvidia GE Force 6200 and my diminishing patience

[Stephen]

Dear All

I have made some changes to my Dell in order to deal with some 
resolution issues.  I have added 1 GB of RAM and now the total is 2 GB. 
  I have replaced the onboard Intel graphics with an NVIDIA GE Force 
6200 with 256 MB of onboard RAM.

Installation of the NVIDIA went OK and I installed the driver
recommended by Ubuntu.  This has allowed me more control over the
resolution which I have set to: 1280 X 720 @ 55Mhz.

However, I now have an entirety new set of problems.  The current
symptoms of which are:
1) windows slow to render if I move them fast across the desktop
2) when too many applications are started the icons and menus become
colour reversed and blured, with menus and icons becoming distorted and
squashed.  Open Office Writer on its  own as the only application open 
  produces this effect.  Other wise it takes FIrefox, Thunderbird and
Kate to bring about the same effect.
3) Sometimes the desktop disappears to blank black screen and a right
click on the desktop brings it back.

When I turned Desktop Effects back on again (with only three desktop 
effects ticked) the problem was worse and with less applications open.

Any help appreciated

Stephen