I'm getting an error using Google Maps API V3 that I don't understand. My initial map displays just fine, but when I try to get directions, I get the following two errors:

Error: The value of the property 'GUnload' is null or undefined, not a Function object

Error: Unable to get value of the property 'setDirections': object is null or undefined

I'm not using GUnload anywhere, so I don't understand why I'm getting that error. As far as the second error is concerned, it's as if something is wrong with the Directions service.

Here is my code:

var directionsDisplay;
var directionsService = new google.maps.DirectionsService();
var map;
function initialize(address) {

  directionsDisplay = new google.maps.DirectionsRenderer();
  var geocoder = new google.maps.Geocoder();
  var latlng = new google.maps.LatLng(42.733963, -84.565501);
  var mapOptions = {
   center: latlng,
   zoom: 15,
   mapTypeId: google.maps.MapTypeId.ROADMAP
 };
 map = new google.maps.Map(document.getElementById("map_canvas"), mapOptions);
 geocoder.geocode({ 'address': address }, function (results, status) {
   if (status == google.maps.GeocoderStatus.OK) {
     map.setCenter(results[0].geometry.location);
     var marker = new google.maps.Marker({
       map: map,
       position: results[0].geometry.location
     });
   } else {
     alert("Geocode was not successful for the following reason:  " + status);
   }
 });
 directionsDisplay.setMap(map);
}

function getDirections(start, end) {
 var request = {
  origin:start,
  destination:end,
  travelMode: google.maps.TravelMode.DRIVING
 };
 directionsService.route(request, function(result, status) {
  if (status == google.maps.DirectionsStatus.OK) {
    directionsDisplay.setDirections(result);
  } else {
    alert("Directions cannot be displayed for the following reason:  " + status);
  }
 });
}

I'm not very savvy with javascript, so I could have made some sort of error there. I appreciate any help I can get.