When I'm writing, I don't seem to remember as many dreams, but I wake up with solutions to plot problems. I'll wake up and think, "Augustine did it!" I can only assume it's because of forgotten dreams. I find it fascinating how our subconscious mind works overdrive while we sleep and sorts things out that we could never do while awake.
I can somehow relate to that. I only remember, what I was dreaming just before I woke up. And I often have new ideas to strengthen existing chapters and for coming chapters. A dream showed me, that my second female character were thinner than paper and I knew, that I had to put some meat on her ;-)