Changing display settings results in reboot

[SolarCatcher]

The warning in PCBSD Control Panel -> Display looks clear: Session will be terminated. I assume this should mean the X-session. However, in my case it always results in a complete reboot of the laptop. This is certainly not intended.

Furthermore, the semi-automatic display configuration does not seem to work for me: I use a ThinkPad x60s Laptop in a docking station with a large external screen attached. No matter what I enter in the dual-head settings, I always get the same small resolution of the laptop screen also on the external screen.