In case it help track down the problem:
I have no video in/out cards and my After Effects CC install has no 3rd party plug-ins at all. In fact I uninstalled and re-installed it yesterday, so it’s fresh-out-of-the-box, but it didn’t help.
I can import/edit/play QuickTimes in Premiere CC – no problems there.
I have QuickTime 7.6.6 installed (as well as the useless crappy QuickTime X which I never use). I have Final Cut Pro 7 installed, and no FCPX. FCP7 installs the “pro” codecs (such as ProRes) but I suspect that the standard OS install (QuickTime X) does not have those codecs. I’d imagine that an FCPX install would include the pro codecs too.
I used the beta version of AE a couple of months back for a job involving a lot of QuickTime renders, and had no problems…but that was on a different Mac (exactly the same spec, same OS, same RAM, same video cards, but a different physical machine…in a different country).
– Paul