Problem in calling web service from javascript at FaceBook

Question

I have an application released at facebook platform (Iframe application) at the following link FaceBookGame Application and the problem now is that i am using ajax technique in the application by calling web service from javascript and i have created the web service and allowed the web service to be called from script by preceeding the web service class with :

[System.Web.Script.Services.ScriptService]

And at the client side i am using the following code :

  <asp:ScriptManager ID="ScriptManager1" runat="server">
     <Services>
        <asp:ServiceReference Path="HMService.asmx" />           
     </Services>     
  </asp:ScriptManager> 
var ret = HMService.HelloWorld(OnCheckComplete,OnFailed,OnTimeOut);     
function OnCheckComplete(arg)    
{
        alert(arg);    
}       
function OnFailed(arg)    
{
        alert(arg);    
}         
function OnTimeOut(arg)    
{
        alert(arg);    
}

And it reports to me the following javscript error in IE :

HMService is undefined

or may be the page clashed at the IE and in firefox it doesnt report to me any error but the calling to the web service is not done but in IE may be the page clashed (and this is not because the calling of web service) or reports javascript error that the HMService is not defined

So i don't know why it is not working at facebook platform is the problem from my side or from facebook platform and it requires to add specific code to be working well???

Hope that i will find a solution to this bug here and thanks for any response