Hi everyone,
I encounter this problem and it's quite annoying, after writing on a input text that is data-binded to the model I have to click twice the button that is on the same div group. Here I provide a JSFiddle that shows the problem, if you remove the data-bind on the input text you don't have to click twice the button to fire the action.
http://jsfiddle.net/MKZfr/3/