I ran into this exact scenario tonight.
I started working on a track, and had some decent success, I was finding elements I wanted to put in the track easily, and I made them fit together well, I was really feeling it, but then out of nowhere, I hit a wall. Now I saved the project, and had to get away from my production area. I don't know how to best fight past that and keep working on it, or just keep working on music in general.
I'd love to hear your tips on this all too often occurring problem.