I don't know if I believe in writer's block - but I'm having a hell of a time coming up with an idea for a new story. My problem is that when I THINK about the story I can't get it, but when I let my mind go usually the idea will just COME to me. I've gotten ideas from random bits of conversations, a line on a tv show, overheard conversations, and dreams. Actually, I think some of my best story ideas have come to me in dreams, including the opening image of my novel. I can force creation, I certainly ask my students to do it, but I tend to find the story isn't as solid unless I have the big idea in my head already.
So, big idea, I'm waiting for you!