One of the most common problems with any video editing software is the preview lag- a result of high quality video slamming your CPU. There is a great fix in Sony's Vegas editing software to allow previews to run full-frame with a slight tweak called the dynamic RAM preview feature. This is especially useful if you don't have a brand new computer with maxed-out RAM and video card. Double-click the clip (or drag for a series of clips) that you would like to preview and select which quality you would like to preview it in. The higher the quality, the longer the render time. Now press Shift + B and the clip will preview at full speed (that is once the render has completed) with the lag.