I had this happen often while I was studying math. I would wake up in the morning with the answer. One time, the answer I "dreamed" was so simple I was ashamed that it had taken me a week to find. I sheepishly turned in my one paragraph proof, and didn't tell anyone how hard it had been for me to complete. The next day I learned that of those who had managed to finish the proof at all, the next shortest proof was three pages! I was able to dream the concept in the simplest of terms, but couldn't find my way through it during conscious thought. I find the correlation between creativity and mathematical thought very interesting. Creativity and abstractness are somehow related.