Version:            (using KDE 4.2.4)
OS:                Linux
Installed from:    Debian testing/unstable Packages

I am using debian/sid (sidux) with KDE4.2.2 first and currently KDE4.2.4. The grafics card is a GeForce 7300 LE, using the latest stable nvidia drivers. I have 3x6 desktops activated and after some time many open windows. Mainly icedove, iceweasel, konsole windows and especially I am using nedit a lot, that has problems when using composite, if it is not started with an option 
  -xrm '*visualID: default' 
(I do not know if nedit is the problem here, I just wanted to mention it.) The PC usually is not turned off (only for dist-upgrades) and so KDE is running for several days or few weeks in one go. Effects speed is set to instant.

I have two problems with KDE4. After a while (some hours or perhaps 1 or 2 days) windows do sometimes no more refresh. They look frozen. But when resizing them, the content is refreshed again once so you see the application is still running.

In this situation sometimes another problem shows up: When opening a new window (I saw it with thunderbird/icedove windows or firefox/iceweasel windows, maybe others?) it was completely black, looking like an empty plasmoid window. Resizing the window does not help.

The only thing that helps in such a case is to turn off compositing effects. With this, KDE continues to run fine without any further problems. Sometimes you can turn on effects again and continue working, but in most cases this does not last for long and you have to turn off effects again. (I am using alt+shift+F12 to turn off/on effects.)

I do not have an idea what could be the problem. So I do not know what kind of information could be interesting to track this down?

On another PC (sidux; nvidia GeForce 6200) I never had such problems. Here only 3x2 desktops are configured and the PC is only running for some hours. Much less windows are opened.

I have the feeling that the KDE uptime is the main problem, but I do not know. Is this a known problem? Which information could be interesting? I am curious about KDE4.3 if this might be already could be fixed there?