Services 3 and node locations
var node = {
                title: "Sample Location",
                body: { 
                    und: [{
                          value: 'Sample Body'
                          }]
                },
                field_location_type: {
                    und: [{
                          latitude : '37.4861987023',  
                          longitude : '-122.2312',
                          country_name : 'United States',
                          province : 'CA',
                          city: 'My City',
                          postal_code : '12345',
                          name : 'Place Name',
                          }]
                },
                type: 'location',
                language: 'und',
            };


This sets a variable 'node' for Javascript. CCK field is "location_type". All the other parameters are being inserted into the node (city, postal_code,...) , but the Lat/Lon is still not being posted. I suspect that it may be because a node can have many 'locations'. Any help here would be great.

Take a look at the debug log: admin/reports/dblog for the json interaction. You need to turn on Services Debug "Debug mode enabled" located at admin/structure/services/list/api where 'api' is the endpoint.