Writer's block

A big fat roadblock, that's what this is! The first weeks of June were productive to the extent of being misleading; I felt a book could be done by October or November. The last weeks have been rather eyeopening. Nothing more than a hundred words, and a genuine problem. Do I continue on the same story, or do I move on to a new one, having more zest. And it doesn't help that my concentration has completely shattered. Cant spend even ten minutes trying to think on the story without any unrelated thoughts creep in and cause train wrecks in my mind.