[Tim Wood]

I'm not seeing this; I tried setting Austria (German) under 10.5, selected an action in Project mode (with no dates set) and entered "20.11.2007" in the start date field.

Could you post a screen shot of your International > Formats system preferences pane and any more details about exactly what you have selected, and what you are typing into the field? Rowan might have a better idea about what could be going wrong since he's Lord of the Dates.