I don't really believe in writer's block per se. I think it's kind of an excuse. Sure, everybody ends up staring at an empty screen, sometimes for a disproportionately long time. But the temptation to write that off as "writer's block" is too great because it's easier than forcing yourself to pound away at the problem one word at a time. I just treat it like 7th grade typing class: hunt and peck until that sticky paragraph is done. And usually the sticky part is not much more than a paragraph.