JQuery UI autocomplete FireFox 编码格式不正常

我的网站用的是gb2312的编码格式,但是ajax传递必须用utf-8，下面是我的写法,在ie7下测试通过,但是在FireFox下就是不行,根据调试得之传过去的是乱码,怎么解决请教高手大大!!
这是客户端脚本:
    $(function(){  
        $("#txtTest").autocomplete({  
        minLength:1,  
        source: function(request, response) { 
            $.ajax({ 
                    url: "jquery/GetAllWords.ashx", 
                    dataType: "json",
                    contentType: "application/x-www-form-urlencoded; charset=utf-8",
                    data: "term="+request.term, 
                    success: function( data ) 
                    {
                        response( data );                    
                    }                            
                });            
            }        
        });    
    });服务器端GetAllWords.ashxpublic void ProcessRequest (HttpContext context) 
    {
        if (context.Request.QueryString["term"] != null && context.Request.QueryString["term"] != "") 
        { 
            context.Response.Clear();
            context.Response.Charset = "utf-8";
            context.Response.Buffer = true;
            context.Response.ContentEncoding = System.Text.Encoding.UTF8;
            context.Response.ContentType = "text/json";
            context.Request.ContentEncoding = System.Text.Encoding.UTF8;
            context.Response.Write(GetLikeUserName(context.Request.QueryString["term"]));
            context.Response.Flush();
            context.Response.Close();
            context.Response.End(); 
        }
    }