Weird Shadeing Problem.....

For some reason , when I put my model in the sim...I get this weird shadeing effect. There are parts of the model that are dark, and parts that look as they should. Has anyone else had this problem? I really need some help.
You can see in the screen shot that there are obvious parts that are not supposed to be shaded like that!
Click on the link to see the pic!
Alan
http://www.fs2004.com/forums/index.php?act=ST&f=71&t=40098
You can see in the screen shot that there are obvious parts that are not supposed to be shaded like that!
Click on the link to see the pic!
Alan
http://www.fs2004.com/forums/index.php?act=ST&f=71&t=40098