I'm working on an effect at the moment which turns a guy's eyes black, heros style.
I motion tracked each eye individually, copied the tracking info to a null. I then made a couple black solids which I masked crudely, added a couple of mattes so the black is just in his eyes plus some other bits to sell it.
Now in RAM preview it looks great but when I render the tracking goes wrong and the new eyes drift off like they they are a few frames forward.
I'm working with 6.5 still (skint) on my Mac Pro, the video is Apple Pro Res 422 at 25fps 1920 x 1080. Anyone have any ideas?
You SHOULD see the same thing in your RAM preview and your final render... I'm guessing that you have motion blur enabled on the layers, but you haven't toggled the switch to display it in your comp (and therefore your RAM previews). When you create the render, since the layer has motion blur enabled, the blur is being applied and making it look like it's timed incorrectly.
If you DO have motion blur enabled on the layers, also enable the main motion blur toggle (at the top of the Timeline palette) and see what happens. You can adjust motion blur settings in the Advanced tab of the Composition Settings (Ctrl/Cmd + K)