Index: public/javascripts/selectmultiple.js
===================================================================
--- public/javascripts/selectmultiple.js        (revision 6519)
+++ public/javascripts/selectmultiple.js        (working copy)
@@ -63,13 +63,15 @@
        },
        setValue: function(value_string){
                this.numberOfCheckedBoxes = 0;
+    this.checkboxes.each(function(checkbox){
+      checkbox.checked = false;
+    });
                (value_string.split ? value_string.split(this.options.valueSeparator) : value_string).each(function(value){
                        this.checkboxes.each(function(checkbox){
                                if(checkbox.value == value){
                                        ++this.numberOfCheckedBoxes;
                                        checkbox.checked = true;
-                               }else
-                                       checkbox.checked = false;
+                               }
                        }.bind(this));
                }.bind(this));
                this.scanCheckBoxes();
@@ -140,4 +142,4 @@
                }
        }
 });