Maybe not so much writers block as periods of indecisiveness - sometimes theres soooo many ways to do something, it can be hard to decide the best way or the easiest way to do it. Or if a problem is complex, it can be hard to pull the trigger and commit to a way to do something.

If I find myself starring at the screen for more then 10 minutes and not writing a single line, I try to walk away - don't open a news site and waste time - literally walk away and go do something completely different. Take a walk, go for a bike ride, clean the house, take a shower, make something with your hands, whatever you do. Your mind will work on the problem in the background - it helps me often.