Writer's Block and how to find a way out of it

Philip Pullman doesn't believe in it. "Carpenters don't get carpentry block." He argues that we shouldn't be so precious about what we do. Instead we should just treat writing like a job of work and get on with it.
James Kelman's advice boils down to the same thing. He says that the only way to defeat the blank page is to write even when it's the last thing you feel you are capable of doing. Even when all you can write is - I don't know what to write. The mind hates a vacuum and something will come out of it...not a very good something perhaps, but something all the same and writing always has to be better than not writing. Remember the wise words of the great short story writer Katherine Mansfield.

Far better to write twaddle or anything, anything, than nothing at all. 

And inspiration only strikes when you are already at the keyboard or have a pen in your hand.Jonathan Franzen has a different take on the subject. In a question and answer session at the famous New York creative hub, Gotham City Workshop, he says that it could be a sign that you're writing the wrong thing.

It happens when I'm trying to write something that I'm not ready to write, or that I don't really 'want' to write. And there's no way to discover my unreadiness or unwillingness except to try and fail.

I would certainly endorse that trying and failing bit. You can't write in your head. It only counts when paper is involved at some stage. All the thinking about a story won't tell you if it works: only putting one word after another can do that.
But I think perhaps we do need to give ourselves permission to have a break from a story that is being particularly difficult. If it is stuck then staying around may make the the mud thicker and stickier....but it has to be a real break: not writing doesn't count. You have to take the writer part of yourself off to a different world and a different story. Only then will you be able to see if you need a holiday or a divorce.
Click on the title of this post to read all of Franzen's Q&A session