Some more information: The problem (X-server crashes on user login) only arises, if "xrender" is selected and the option "kein Startbildschirm" (=no splash screen) is selected.
As long as I select something else than "xrender" (e.g. OpenGL 3.1) in "Arbeitsflächen-Effekte" (=desktop effects?) or as I select a splash screen, I can login without crashing X. Interestingly only one of two mashines suffers from this: It is a laptop with Broadwell chipset. The other computer has Skylake and works well under the same settings. Both run jessie with xserver-xorg-video-intel from jesie- backports. Hope this helps. Juergen
