Hi,

an alternative way to reproduce it, is to just wait for screensaver. Only the backlight is off, it is possible to see the image on LCD matrix if you get the angle right.

The system is the by now fairly old Dell XPS M1330, 64 bit kernel, KMS used (and works since 2.6.35), no 3D. There is sadly nothing interesting in dmesg or in XOrg.0.log (attached along with .config anyway). The repo's HEAD is at f6614b7bb405a9b35dd28baea989a749492c46b2.