Lag during clip playback in Premiere Pro CS5 I am using the 30 day trial of Premiere Pro CS5 trying to edit some clips of some game footage. The clips are in 1680x1050 and are roughly 3.5GB each. 

All the clips are saved on to my external USB 3.0 hard drive, which I've also set as the scratch disk in Premiere. 

The clips will usually lag for the first 3-4 seconds, and then play smoothly for the remainder of the clip. Sometimes it begins lagging briefly in other parts.

So I would like to know what the optimal set up for video editing would be. 

Here are my computer specs:


CPU: AMD Phenom II x4 965 Quadcore, 3.4 GHz
GPU: ATI HiS IceXQ Radeon HD 6950 with 2GB DDR5 memory 
RAM: 8GB G.SKILL Ripjaws RAM 
OS: Windows 7 Ultimate x64 (On a 3GB/S Sata HDD) 
Verbatim 1TB USB 3.0 External HDD (Scratch Disk, file source)
Have you rendered the work area? Unrendered clips can lead to lag in the playback.

If you have rendered your clips the bar above your clips in the timeline should light up green instead of red or yellow (see picture below). 



If the bar isn't green, go to Sequence->Render Entire Work Area.

Done!