谷歌地图没有出现在IE7/8中(但在IE9中有效)

我正在使用googlemapsapi3来显示加拿大的Google地图和一堆标记,但是在IE7/8中,它根本没有显示出来,只是给了我一个灰色的矩形。它在Firefox/Chrome/Opera/IE9中加载得很好。

代码如下:

$(document).ready(function() {
    var browserSupportFlag = new Boolean();
    var map;
    geocoder = new google.maps.Geocoder();
    var myOptions = {
        zoom: 3,
        mapTypeId: google.maps.MapTypeId.ROADMAP,
        navigationControl: true,
        mapTypeControl: true,
        scaleControl: true,
        streetViewControl: true,
        navigationControlOptions: {
            style: google.maps.NavigationControlStyle.ZOOM_PAN
        },
        mapTypeControlOptions: {
            style: google.maps.MapTypeControlStyle.DROPDOWN_MENU
        }
    };
    //var bounds = new GLatLngBounds(); 
    map = new google.maps.Map(document.getElementById("dealer-map"), myOptions);

    if (navigator.geolocation) {
        browserSupportFlag = true;
        navigator.geolocation.getCurrentPosition(function(position) {
            currentLocation = new google.maps.LatLng(position.coords.latitude, 
                                                     position.coords.longitude);
            contentString = "Location found using W3C standard";
            map.setCenter(currentLocation);
        }, function() {
        });
    }
    var geoXml = new geoXML3.parser({ map: map });
    geoXml.parse('<?php echo "/dealers.php"; ?>');

});     

<script type="text/javascript" src="http://maps.google.com/maps/api/js?v=3.1&sensor=false&region=CA"></script>

HTML/CSS是:

<div class="main-content">
<div class="wide-content">
<h3>Find a Dealer</h3>
<div style="width: 800px; height: 330px;" id="dealer-map"></div>
</div>
</div>

知道怎么回事吗?