Unable to Post Xml using ajax to WCF method

hi,
I am getting Xml  from third Party.(Working in C#)
After Removing  Special characters from xml I send it to WCF Method Using Jquery Ajax method.
But i am Unable to make hit to service method for some user Xml.
special character i remove :
      str = str.Replace("\"", """);
        str = str.Replace("&", "&");
        str = str.Replace("<", "&lt;");
        str = str.Replace(">", "&gt;");
        str = str.Replace("'", "&apos;");
Can anybody suggest what thing i am missing.????



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