External USB keyboard does not work when connected to Dell Dockingstation on boot

Today we had the problem that we can not enter the Truecrypt password on the external keyboard connected to a Dell Dockingstation with a new Dell Latitude Laptop. But after we have typed in  the password on the Laptop keyboard  and windows has booted the external keyboard works without problem. We have tried many things like updating the BIOS and other keyboards, but nothing worked. So we compared the BIOS config value by value with a working Laptop and found out that the Setting "Fastboot" in the "Post Behavior" section is the problem. When it is set to Minimal the USB ports are not initialized and the external keyboard is not working, but when it is set to "Thorough" the external keyboard works without problem. So if you have the same problem go and check your BIOS Settings.