Bug fix for another use case, see comment by whittet here: http://bugs.jqueryui.com/ticket/6702

(cherry picked from commit 2bf061e)

Author: whittet

ui/jquery.ui.sortable.js

@@ -50,7 +50,7 @@ $.widget("ui.sortable", $.ui.mouse, {
 		this.refresh();
 
 		//Let's determine if the items are being displayed horizontally
-		this.floating = this.items.length ? (/left|right/).test(this.items[0].item.css('float')) || (/inline|table-cell/).test(this.items[0].item.css('display')) : false;
+		this.floating = this.items.length ? o.axis === 'x' || (/left|right/).test(this.items[0].item.css('float')) || (/inline|table-cell/).test(this.items[0].item.css('display')) : false;
 
 		//Let's determine the parent's offset
 		this.offset = this.element.offset();