Cropped rectangle doesn't work as expected

I have an NSView to draw a rectangle to crop image, and one NSImageView to be webcam (camera preview window).

I want to put the NSView on the NSImageView.

When I take a picture, it can produce a cropped image automatically.

The problem is that when I don't start the camera preview window, the crop rectangle can drag and resize normally, but when I start the camera preview window, the crop rectangle out of control.

I've implemented drag and resize function by mouse event.

How can I resolve this problem?

8/19 update: My code and program video.

code: gist.github.com/536831

video: http://www.youtube.com/watch?v=DLjuBGHh3f8

Thanks!!

Hmm, maybe one of the views has User Interaction Enabled set to NO (default value for UIImageView, for example)?