I will try this with another external monitor later, but I'll provide what I can. I booted in UMS mode by giving the option i915.modeset=0 on the kernel command line - this gives an errror message about an unknown option, but seems to work. I can't reproduce the bug under UMS, so this is a functioning work-around. The xorg.log-file is attached (also with Option "ModeDebug" "yes" set in the xorg.conf).
I will try this with another external monitor later, but I'll provide what I can. I booted in UMS mode by giving the option i915.modeset=0 on the kernel command line - this gives an errror message about an unknown option, but seems to work. I can't reproduce the bug under UMS, so this is a functioning work-around. The xorg.log-file is attached (also with Option "ModeDebug" "yes" set in the xorg.conf).