John McIntyre, Baltimore Sun copy-desk chief, talks about the word disinterested, which has come to be used to mean both impartial and not interested, over at You Don't Say. And he makes the broader point that you should consider your readers and your intent when using a word whose meaning has split:
I can try to help my students by advising to keep in mind the basics of rhetoric: What are you trying to say? Who is in your audience? What words, tropes and strategies will convey your meaning to the reader most precisely, without misunderstanding or distraction? There are choices to be made, and editing is making choices.