Block, as far as I understand it (which isn’t much), usually stems from someone failing to grasp the direction their work is headed. If that’s correct then the source could come from any number of problems: lack of talent, lack of preparation, the wrong choice of project. The cure lies with the malady not the symptom. I try to tackle this briefly in Writing: A User Manual but in truth the answer is one for the individual to find, usually through a better comprehension of the craft. Work, in other words, not a search for a shortcut.