Normally when you click Stop on an item in the render queue, it adds it to the bottom of the list and will pick up where it left off. That may be what you want, but often you intended to bust the render, tweak it, and re-render. To stop a render and re-queue it to begin at the beginning, hold down the Option (Alt) key when clicking Stop Render. This will avoid the pickup and add the item to be re-rendered from the start of the original output settings.