I wasn't sure whether to post this here or in the Firefox forum, since the problem has only started happening since I upgraded to FF15 a couple of days ago.
I can demonstrate my problem if you take the source from the default example for the jQuery UI Sortable plugin at http://jqueryui.com/demos/sortable/ (click on 'View Source') and then add a click function to the script, like this:
i noticed exactly the same problem (after update of FF to 15)
not sure if FF will admit it as a problem/bug inside a browser (as it would have been noticed on many sites already and it seems to be not yet) - so is there any workaround for that (which will not destroy all other browsers handling)?
The problem seems to be that when you drag an item, jQuery removes the element from the DOM and immediately puts it back in. In all browsers except for Firefox >= 15, this prevents the click event from being dispatched. But FF >= 15 can still dispatch the click in that case. Click event behavior in this situation is not really specified in DOM3 events.
Note that if you use just 'draggable' then dragging the item and releasing it will fire the click event, in all browsers.
It's up to the jQuery devs how they think jQuery should behave here. I think it would make sense for 'sortable' to not suppress click events, to be consistent with 'draggable'. If the devs decide that it should suppress click events, I think relying on removing and reinserting the element to cancel the click event is a bad idea.
Having said that, we'll probably change Firefox back to be consistent with other browsers in this case, anyway.