There seem to be a CSS problem with the contextual menulet on a story: when trying to select a social bookmark (usually Google+ for me) under the “Email Story” line, the “story” part of the title jumps to the second line and back, moving the other icons with him. Therefore, the social bookmark icons are impossible to reach.
This does not happen every time, it may have something to do with the place where it pops (it seems to be more frequent when the item you want to share is near the bottom of the page). I have seen it happening with Chrome 28 Windows and Safari 6 Mac.
By the way, it would be a good idea to rename this menu item into something more appropriate, such as “social sharing”.