Ok so you are trying to edit ProRes 4444 on your internal drive ?
Thats the issue. First you do not need ProRes 4444 for 5D footage it creates huge files and you are gaining nothing except a slow system.
Use ProRes LT or 442.
Secondly never edit directly on your computer - the drive is not fast enough and especially not when you are talking about multiple HD streams.
As a bare minimum you need and external firewire 800 7200 rpm drive.
But bear in mind this is the basic spec, once you start 2,3,4 etc HD layers at the same time you need to look towards faster drive interfaces and raids. You will then find realtime playback performance increases dramatically.
best wishes
Neil
http://www.patience.tv
