check username availability using ajax

 Hi guys,
 I am trying to get a little ajax script working on my site that allows me to check for the availability of a username using an ajax call on my sql database. The code I have below works but it doesn't give me the result value from the webmethod class. I tested my sql statement and that does work. I even took out all the database stuff in the webmethod and just set the bool to true and it still doesn't return the value as true!

in my .aspx page I have the following: 
<asp:ScriptManager ID="ScriptManager1" runat="server" EnablePageMethods="True" />

 <asp:TextBox ID="Username" MaxLength="30" runat="server" onkeyup="usernameChecker(t ...