First guess is that you are connecting the cables to the wrong matching slots, make sure you have the video and audio in the right connections on the TV. If your TV has combination composite and component jacks make sure they are set to the right thing in options to what you are connecting to them. You may want to post some pictures how you have things connected since without knowing what you are doing it's just guessing.
That TV does have AV out as well as in so you could have them mixed up. The yellow video output of the Xbox goes to the Y/Video input. The red and white audio cables to the PC/AV/Component audio input.
As mentioned above if the TV requires you to chose composite or component video you will need to do that or you will get a bw picture.