Problem using a PageMethods funtion

Hello All 
i am using a PageMethods function  to call server side function through JavaScript.  Its work fine
but when i add the setting for url writing in web.config and start the process then PageMenthods does not work .
here is my code in web.config and global.asax
After adding a setting for url writing in web.config i put the code to start the Process in global.asaxand then pageMethods does not work
and if i comment the code in global.asax then  pageMethods work fine
please tell what wrong with this .
 
 
 
Global.asax

 Sub Application_BeginRequest(ByVal sender As Object, ByVal e As EventArgs)
        ThunderMain.URLRewriter.Rewriter.Process()
    End Sub
 
Web.config
<configSections>
    <sectionGroup name="system.web">
    ...