Trust me, we all get it at some point in time, and it's no fun. If you do get it, write some more. Keep your creative juices flowing, because at any moment when you least expect it, you will create the ultimate story idea. My storylines have been sudden revelations when I wake up in the morning. Do whatever it takes to dream at night.
Dreams are an excellent source of ideas, because they are like a movie.
The book On Directing Film by David Mamet explains this idea further. He talks of uninflected images that combine to create a moving story. He correlates dreams to this idea of uninflected images. It is a brilliant book and I recommend it to all writers out there.