jQuery sortable cancel event if not valid

jQuery sortable cancel event if not valid

I have a list which is sortable. Before I start sorting, I want to check
if all the elements of that list are valid. If not, cancel the event and
leave the list intact.
You can find the code here http://jsfiddle.net/DZYW5/4/
When I use this, the event is canceled, but the element is removed.
start: function (event, ui) {
if (!valid()) {
return false;
// it cancel's but the element is removed...
}
}
Maybe I should implement a "beforeStart" event? Suggestions?
Thanks in advanced