Ground vehicles superimposed on aircraft!

Hi. I have a new FSX installation, with acceleration pack (so SP1+2). No addons (yet). I am getting a very odd effect in that small black squares are superimposed upon the fuselage of a/c (outside view, of course) - seems to happens at whatever airport. As you pan around it is obvious that the black squares are the wheels of ground vehicles (baggage carts) behind the aircraft. Here's a screenshot: anyone have any ideas on this?Thanks.Martin