First, sorry for my english, I'm from Argentine. I'm using fedora 13, and my problem is with some of the effects of kwin.
I have installed kde 4.5 RC3 from the "kde-testing" repositories, but my problem starts with kde 4.4.5 wich is the default in fedora 13.
I think that kwin has problems making the miniatures of the windows, because the problem it's the same in the thumbnails on the taskbar, on the windows switcher or in the "Present windows" plugin. The miniatures are highly saturated, and with clear windows (the oposite of dark windows¿?)I only see a white rectangle. I have an intel GM45.
The problem is solved when I put "* Resolution and low cpu" on the options on preferences->style->fine tuning, but i lose some nice effects too. Someone knows what does exactly do this option? I want to know to try to identify the real problem. I used compiz the last year and i dont have this problem.

I had the same problem and unchecked "direct rendering" and the saturation problem was fixed. I would report a bug for direct rendering, but I can't for a while so I would appreciate it if you could.