Are you shooting with ISO set to automatic? You can recover some control by setting ISO to 100, 200 or 400. This will give the camera just shutter speed and flash power to control exposure.
Is it just the foreground that is overexposed? If so, you can recompose to have a different foreground. If you like those foreground elements, then you may have to go to manual to control both aperature and shutter speed.
Patrick Hurley's answer is a very good approach and goes straight to the fix if you are comfortable using the 1000D's menus. (I would comment his answer if I had the rep).