I don't have any severe sleep problems, but I can relate to this issue. I find reading fiction helps. It's kind of difficult to dream about an interesting problem or a project, so the way I perceive the problem is that my brain doesn't slip into a narrative free-associative state. But if I can get myself to think about something "dreamable" then it's a different story. A book works b/c you already need to engage your imagination quite a bit as you read anyway