First, I'm not sure I'm reporting this to the right package (I can't find a Kwin package in the repos).

Since KDE 2.11, Kwin isn't rendering window decorations correctly when an applications first starts. I was waiting for KDE 2.11.1 to be released before reporting, but I just upgraded and restarted and the problem still exists. I've included a screenshot to illustrate.

Kwin appears to render everything right after a window looses focus or something happens within the application to trigger redraw (like entering a folder, or clicking on the desktop or another window), so I know it's not that Kwin can't render the decoration, it just doesn't do it when the app starts. Decorations also get messed up after a window comes of of fullscreen (only worse. aka close/min/max buttons don't render).

I've tried resetting to factory defaults ($ rm ~/.kde4) and played with every combination of rendering backends (GL 3.1, 2.0, Xrender, etc) to no avail. It should be noted, however, that the problem doesn't exist with Desktop Effects disabled. So it appears this is a new bug with the raster backends.