[T400 + mini dock] System won't turn off after undocking

[Mighty_Mauz]

I just got my advanced mini dock and I have some troubles with it. I usually dock and undock without shutting down the system, just only with the right procedure of unlocking the key, push the undock button and then pressing the large physical undock button to undock. But the thing is that quite often the system doesn't want to shut down properly anymore. The screen goes black, but it is still on and I have to press the power button for a few seconds for a hard power off.

Or, if I dock it for a second time, the usb ports don't function, the second screen is working perfectly, but not my mouse.

What I have connected to the docking station:
- vga lcd
- sound from the lcd
- usb mouse
- network cable

Is there anything I'm doing wrong?