"This is not an appropriate use of this tool. Areas of the image may be too wide."
This happens when you use QuickTrace to follow an outline in the picture and then QuickTrace finds a part of the outline that is very thick. This can be caused by excessively broad outlines or by selecting too much of the picture with a high Color Tolerance value. In this case, QuickTrace does not know where to trace the outline as the problem part of the outline is more like a fill area. Use a lower Color Tolerance value, or use the editing functions in the Picture window to make the outline thinner or break up the outline so that the wide parts are isolated from the rest of the outline.