Writer's block is evil. Pure and simple. There is nothing more frustrating for a writer than to be sat in front of your computer/notepad/scroll wanting to work but nothing happens. It's as your brain has gone on strike. Thanks brain! However, I find that for me, to walk away and think about something else works wonders. I like to have two or three "trash scripts" on the go - scripts that will never see the light of day, scripts that are pretty awful, but if I write a lot of nonsense and think of a completely different, story, my original idea will come back to me and I can start again later. It doesn't work for everyone, but I find starting a new piece suits me well.