Your KDE installation appears to be damaged, or there are some files on your system which expose a bug in KDE.
Please verify that kdelibs and kdebase-runtime are correctly installed on your system.

Also, did you install any new applications when you upgraded to KDE 4.2.2?

New installation of debian testing with gnome. After, kde was installed with: 'aptitude install kde-full'.
Now after the 4° icon the mouse cursor becames a big pixel with vertical bars red blue and yellow and the system freeze (hard reset is necessary).
The graphics card is ATI 9600. I've something incompatible in my hardware?
Thanks, Max

This is likely due to a bug in the graphics drivers unfortunately. Are you trying to use Desktop Effects in System Settings > Desktop? If so, try disabling them.

If the system locks up shortly after login, try Ctrl + Shift + F12 which disables them temporarily, and should allow you to use System Settings to switch them fully off.

Unfortunately Ctrl + Shift + F12 does not produce any effect.
I try to change the video driver with the proprietary?

If you are using the ATI driver, try using the "vesa" driver instead. Likewise if using the "vesa" driver, try the ATI one.