The problem with this approach apparently is that unconsciously derived solutions remain unavailable to the conscious mind. That is to say, they remain unconscious. If you find the solution when you are conscious it’s not because you found it before during an unconscious period. The whole solution process was more or less conscious. If you follow this line of thought.
Anyway, for this and six darn interesting ideas about releasing your creativity, most of them less painful to learn about than this one, see the PsyBlog entry “Get Creative: 7 More Psychological Techniques”.