JQuery :: Unbind (Keydown) Not Working Properly

I have a slight problem in FF3.5 that unbind('keydown'); is not working properly..
$("#q").unbind('keydown');
$("#q").keydown(function(e){
var code = (e.keyCode ? e.keyCode : e.which);
if(code==40 || code==38) {
var totalResults=$("#quick-search-results li");
var selectedResults=$("#quick-search-results li.qs-selected");
if(code==40) {
var nodeIndex=($("#quick-search-results li.qs-selected").length<=0) ? 0 : $("#quick-search-results").index('li.qs-selected');
alert(nodeIndex);
}}}); // end keydown

The above code alerts once on first keydown (with the down arrow key [code==40]), twice on the second, three times on the third and so on.. it worked fine in FF3 but a recent upgrade to FF3.5 seems to have broken the functionality..