It sounds like the boot piece in question had more than one material assigned to the piece.

If you select an object, and no material shows up in the material preview window (see picture), then the object has more than one material assigned.

You can split the object into it's various material groups by selecting the object, typing ctrl-e, and selecting the split button.

You can also adjust materials by using the Material Summary. Press F6 to bring up the Material Summary window.

Charles

Charles