We recently ran into this issue when on the same page there is a Like button and a Login to Facebook button. Only the link for the Like button works. The link for the Login button doesn’t. This is strange at first, because the Login button is working on any other pages. Doing a little more reading, we found out that if you have the “all.js” javascript called twice it will cause this issue. Once we removed one of extra javascript calling to the “all.js” file, both buttons are clickable and working.