Hello, I have a custom built machine with Win 64 and Nvidia GTX 660. All my video is jerky on occasion. Games (Star Wars, Guild Wars, WoW), Hulu and Youtube. Not only is the video jerky, but the sound sputters. I've updated my driver and installed a different anti-virus software on the advice of my technical person. He is out sick for 10 days, what else can I try?