Does Writer's Block Exist?

Writer's block is a disease for which there is no cure, only respite. ~Laurie Wordholt

I have a very productive writing friend that says there's no such thing as writer's block we just make excuses not to finish work. But in the last week, I had such a resistance to a piece of writing that nothing was going to help. I spent hours rewriting one sentence, only to edit it out in the end. Sometimes I think its better to face another blank page instead of trying to rewrite something that isn't working.

What are your thoughts?
The Writing Nag