Traversing XML Tree - Two Variables?

I have the following XML:
Code:
<root>
<MemberProvider name="myName">
<Marker>
<Latitude>-32.025469</Latitude>
<Longitude>115.950136</Longitude>
<Name>Beacon Lighting</Name>
<Address>219 21 William Street, Cannington WA 6107</Address>
<Phone>08 9356 6422</Phone>
<savingText>Members get 10 off RRP</savingText>
<disclaimer>Also save 10 off grid connected solar power systems</disclaimer>
</Marker> ......

Now in my Javascript, I have
Code:
var xmlrows = xmlDoc.documentElement.getElementsByTagName("Marker");
var xmlGroups = xmlDoc.documentElement.getElementsByTagName("MemberProvider");
//for the number of Member Providers listed
for (var i = 0; i < xmlrows.length; i++) {
var xmlrow = xmlrows[i];
var singleGroup = xmlGroups[i];
var xmlcellLongitude = xmlrow.getElementsByTagName("Longitude")[0];
var xmlcellLatitude = xmlrow.getElementsByTagName("Latitude")[0];
var point = new GLatLng(parseFloat(xmlcellLatitude.firstChild.data), parseFloat(xmlcellLongitude.firstChild.data));
//get the name
var name = singleGroup.getElementsByTagName("MemberProvider")[0].getAttribute("name");

Why do I have two variables loading the xml doc? The first appears to work, but the second (xmlGroups) does not. Every time I try and get the Name attribute from the MemberProvider node, it throws getElementsByTagName("MemberProvider")[0].getAttribute("name"); is null or not an object.