We have received a couple of reports of this type of problem, but have not yet been able to reproduce this problem.
Another user reported being able to work around the problem, in this forum thread:
I am having this exact same problem with the 8-core MacPro. I ended up fixing it by going to System Preferences, Mission Control, and disabling Displays have separate spaces
This is not ideal at all, but, for the sake of editting and compositing, it's what needs to be done.
Funny, depending on where the Menu bar was in System Preferences, Displays, Arrangement, - the opposite monitor would contain the Video Preview. That was an easy enough fix, but, this would only happen if I had After Effects in that space "Space" or "Monitor." The moment I moved AE into the opposite monitor the video preview would disappear.
Please let us know if changing the OS preferences resolves the problem for you.
Hey, it works, Tim! Thanks for that tip. I have not even bothered with Mission Control before. I haven't seen the usefulness of it.
When I switch to Pr, the full-screen image switches with it, the way it's supposed to. Great!
Glad it's working.
Because we haven't been able to reproduce the problem locally, could you do me a favor and provide a screenshot of your System Preferences > Mission Control and Display settings? I'll try to match your configuration here and file a bug if I can isolate the correct factors.
Thanks. But, shoot, my fault I wasn't specific enough: I meant to ask for the Arrangement tab of the Display prefs. Also, the Options tab; that is unique to the Apple Cinema Displays (at least, I don't have it with my HP and Dell displays).