I'm having trouble editing MPEG files. When I play them back, and when I burn them, the video tends to skip, or playback jerky. I've already tried adjusting the cache. I dont know what else to try. I'm using Movie Edit Pro 14 on a Dell with an AMD Athlon Dual Core 5600+ 2.80 GHz, with 4GB RAM and nearly 200 GB of hard drive space. Help!