The following seems to have fix many problems of slow 2D in KDE 4.x ( at lest without opengl enabled, I don't use Nvidia's opengl in their driver):
This was suggested by mick232 in this post http://www.nvnews.net/vbulletin/show...2&postcount=22
Type in a console "nvidia-settings -a PixmapCache=1"
That controls whether pixmaps are allocated in a cache.
Then type in a console "nvidia-settings -a PixmapCacheRoundSizeKB=(some size in KB for how large you want the pixmap cache to be, e.g. 16000)"
That controls the number of kilobytes to add to the pixmap cache when there is not enough room.
Also mick232 suggests:
I also have a cron-job in place that flushes the pixmap cache every 20 minutes (by turningit off and on again):
nvidia-settings -a PixmapCache=0
nvidia-settings -a PixmapCache=1
It seems the cache got fragmented or thrashed after a while which might have caused the sluggishness.
If you want to get a list of all your card settings type the following ion a console:
nvidia-settings -e all