I see this bug as well on an Lenovo T420. This bug does exist in wheezy. I can work around by simply downgrading to linux-image-3.2.0-4-amd64=3.2.35-2 Which I get from: deb http://snapshot.debian.org/archive/debian/20130101/ wheezy main I get this problem using KDE with or without the composition. Pretty much any activity (i.e., scrolling in konsole) triggers it. The system is totally unusable. Charles