I have a problem - if I have too many windows open with compositing enabled, and then I open another window, it does not repaint. This means that if I have, for example, 20 windows, and I open another one, it is either completely black, or it shows the contents but nothing can be clicked. If I resize that window and make it smaller, however, it starts working. When I maximize it, it stops.

So the only way to make things workable is to either close some windows or disable compositing.

Anyone encounter that problem before and know how to solve it?

My video card is NVIDIA GeForce Go 7300.

You're most likely out of video memory. Please run `kwin --replace` in a terminal and read the output logs once it happens again (If the terminal itself doesn't update use Alt+Shift+F12 to disable compositing).

Sorry I didn't notice your reply...

Where are the output logs?
If I do "kwin --replace" nothing is printed out...

I guess you will need to install the KWin debug packages to get the logs.