If someone sends you a file and you accidentally close the tab before pressing the button, then it just sits in your transfer window waiting to start with no way of acceptance.
Perhaps we need a little confirm button in there as well because if its already open and someone sends you a file then you get a list item appearing with the attention grabbing bar so your leading user attention there but without a way to accept it.
Also the button in the message window should disable once its been clicked.
Maybe I'm thinking over the top for the first point, but the button really should disable
