C# - WCF Service Returns 400 Bad Request

I've got this application that works locally and when deployed and using a .mdf SQL Express database file (which I usually use for testing purposes). However, when I change it to work with our SQL Server 2008 the app works but the service doesn't. For example if in my code behind of a page I have a button that adds data to a table such as this it works fine:

public static string connString = @"Data Source=server1;Initial Catalog=Project;Integrated Security=True";
protected void btnAddProj_Click(object sender, EventArgs e)
{
using (var sqlc = new SqlConnection(connString))
{
sqlc.Open();
var cmd = sqlc.CreateCommand();
int intProjectID;
// Add the project info to the database
cmd.CommandText = "INSERT INTO tblProject VALUES(@ProjName,@ProjTeam,@ProjStart,@ProjEnd)";
cmd.Parameters.Add("ProjName", System.Data.SqlDbType.NVarChar).Value = txtProjName.Text;
cmd.Parameters.Add("ProjTeam", System.Data.SqlDbType.Int).Value = ddlTeamSupported.SelectedValue;
cmd.Parameters.Add("ProjStart", System.Data.SqlDbType.NVarChar).Value = txtStartDate.Text;
cmd.Parameters.Add("ProjEnd", System.Data.SqlDbType.NVarChar).Value = txtEndDate.Text;
cmd.ExecuteNonQuery();
}
}

My web.config is setup to use impersonation on that server and all works perfectly well. However, for my service the query doesn't seem to return anything and I get a 400 Bad Request error. The code for the jquery is:

$.ajax({
type: "POST",
async: false,
url: "Services/ProjectService.svc/test",
contentType: "application/json; charset=utf-8",
dataType: "json",
success: function (data) {
console.log(data);
}
});
And for the Service:
[ServiceContract]
public interface IProjectService
{
[OperationContract]
[WebInvoke(ResponseFormat = WebMessageFormat.Json)]
ArrayList test();
}
public static string connString = @"Data Source=server1;Initial Catalog=Project;Integrated Security=True";
public ArrayList test()
{
var sqlc = new SqlConnection(connString);
sqlc.Open();
var cmd = sqlc.CreateCommand();
cmd.CommandText = "SELECT ProjectID FROM tblProject";
var reader = cmd.ExecuteReader();
ArrayList temparray = new ArrayList();
while (reader.Read())
{
temparray.Add(reader[0]);
}
sqlc.Close();
return temparray;
}

If instead of querying the database I have the service just return static data then it works fine. What could cause my service not to be able to connect to the database when the rest of the code behind for the app works?