Hi there

Im having a bit of a problem getting some Javascript on my html page working properly

This is my Html File

Code:
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<script src="javascripts/jquery-1.9.0.js" type="text/javascript"></script>
<title>Invoices</title>
	
</head>
<body>
	<Script type="text/javascript">
	function GetVehicles(){
		$(function(){
			var regpart=document.getElementsByName('serstr')[0].value;
			var items="<option value='0'></option>";
			$.getJSON("phpscripts/refreshvehicles.php?a="+regpart,function(data){
				var item="";
				$.each(data,function(index,item){
					items+="<option value='"+item.VehicleId+"'>"+item.Vehicle+"</option>";
				});
				$("#a1_vehicle").html(items);
			});
		});
	}
	function GetInvoices(sel)
	{
		$(function(){
			var vid=sel.options[sel.selectedIndex].value;
			var items="<p>"+vid+"</p><br>";
			items+="<table border=\"1\" cellspacing=\"0\" cellpadding=\"2\">";
			items+="<tr><th>Invoice Number</th><th>Invoice Date</th><th>Amount</th></tr>";
			$.getJSON("phpscripts/getinvoices.php?a="+vid,function(data){
				var nitem="";				
				$.each(data,function(index,nitem){
					items+="<tr><td>"+nitem.InvoiceNumber+"</td><td>"+nitem.InvoiceDate+"</td><td>"+nitem.Amount+"</td></tr>";
				});
			});
			items+="</table>"
			$("#a1_invoice").html(items);
		});
	}
	</script>
	<form>
		<fieldset>
			<legend>Select Vehicle</legend>
			<input type='hidden' name='submitted' id='submitted' value='1'/>
			<label for='serstr' >Vehicle:</label><br>
			<input type='text' name='serstr' id='serstr'  maxlength="50"/><br>
			<input onclick="GetVehicles()" type='button' name='Filter' value='Filter'/><br>
			<label  for='vehicles' >Vehicle:</label><br>
			<select onchange="GetInvoices(this)" id="a1_vehicle" name="a1_vehicle">
				<option>Default</option>
			</select>
		</fieldset>
	</form>
	<div id="a1_invoice" name="a1_invoice">
	</div>
</body>
</html>
My Php Script definatly works and echos the JSON as expected see here
but id say its the $.getJSON("phpscripts/getinvoices.php?a="+vid,function(data) bit thats not working as i have played around putting other Html Rows in during that section and they haven't come out

Many thanks for any help

Ian