OK..... so I have a pretty beefy machine. But this problem doesn't have to do with my machine, but with the way CS5 has changed the way it looks at comps. In CS4, if I needed to make a quick patch, I could place the previously fully rendered file on the top of the comp. Knock a hole where my change/patch needed to take place, and then render it off again. CS4 would clip along at a fast pace.... ignoring all the layers below the top rendered file. As it should. However... CS5 has gone backwards and no longer ignores the layers below the rendered QuickTime. Even though there are no alpha holes or the like. Just a solid rendered QuickTime.