When Charlie and Jodi are sitting in the theater and reading their names in the newspaper, from the back view, Charlie has his arm around Jodi's back. When he sees Cooper coming, he takes it off and it falls to his side. Then, when Cooper talks, it shows the front view of them, and his hand is back on her shoulder even though he had just taken it off.
I remember that scene, and I think Cooper gets all cocky with him, so, to show that he (Charlie) has Jodi at the moment, he puts his arm BACK around her. Of course, I may be wrong, but that's what I remember.
I just got done watching the movie and this is definitely a slip-up!! You see Cooper talking to Jodie and Charlie and first he has his arm around her. Then Charlie takes his arm back from around her neck. It is very clear that this happens. You see him take it away from a back view and then they show him again from a front view and its still not there. Then the camera switches angles again to a back view and its there. You see his arm throughout the whole time and never did you see him put it back around her neck after he takes it away. It just mysteriously (not really mysteriously but you know what I mean) comes back.
This is a slip up. It shows Jodi and Charlie from the back, with his arm around her. Cooper walks up and Charlie moves his arm. The shot goes to the front of them and Charlie's arm is behind her now. It's totally a slip up.