Bugs, bugs, bugs...and more bugs. Probably one of the most annoying parts of development in general is having a bug that is causing a lot if not the entire thing to malfunction. Sometimes its the simple things, like a missing comma or semicolon. Others its the more major things where you just have no idea why it's broken.
Personally I like to step away from my machine and desk, either grab something to drink, eat, and the occasional scream outside in my back garden. As well as taking long (very long) stress walks to help clear my mind, I often find that half way through a track I'll come up with the solution in my head.
So, what do you do?