At least once each week, one of our (about twenty) developers gets caught by this bug.
I.e. kwin is still running, we can raise/lower windows, but it is impossible to move or resize them. Running kwin --replace does fix the move/resize issue, but we would ery much like to see the bug fixed!
We are running RHEL4, and reported the bug to RedHat two years ago, but haven't got much of a response (i.e. they kept asking for more and more information until we gave up).
We still don't know what triggers the bug - we cannot reproduce it - but we have seen it more than a hundred times.
One would believe that such a central component of KDE should get fixed sooner, but apparently not...