This problem applies to all objects with motion paths. It happens when selecting selecting a different object in the scene and then selecting the object with the motion path right afterwards will somehow generate a duplicate palette and motion path that "lingers." A work around that sometimes works would be to deselect all objects or select just the Scene from the instances palette and move to another room (i.e. modeler, renderer, storyboard) and then select the object with the motion path. Do not select another object in between. If this doesn't work you could also save the project and reopen it and then select the object with the motion path. This usually will get rid of the extra motion path and palette but you must avoid the sequence of selecting one object and then the object with the motion path otherwise the duplicate will pop up again.