New to AE? I bet you are.
You may have plenty of editing experience, but AE doesn't work like an editor. I strongly recommend that you become well-versed in the logic behind the way AE functions, which you will find at the top of this page.
> but cs5.5 AFX won't take it
What happens when you try? Do you get an error message?
Do you have the ProRes codecs installed on the computer that you're using?