这是什么错误啊？

Microsoft VBScript 运行时错误 (0x800A005E)
无效使用 Null: 'replace'
/web/product_Look.asp, 第 116 行


代码是：  <%
           
        Set rsNews = Server.CreateObject("ADODB.RecordSet")
  Set rsCate = Server.CreateObject("ADODB.RecordSet")
  
  Set rsNews = Conn.Execute("SELECT * FROM Detail WHERE  id = " & Request.QueryString("id"))
  If Not rsNews.EOF Then
    
    txtcontent = rsNews("Product_Intro")
    txtcontent = replace(txtcontent, "<br>", chr(13))
    txtcontent = replace(txtcontent, "&nbsp;", " ")
    rqtContent = replace(txtcontent, "''", "'")
    
    rqtProduct_TX = rsNews("Product_TX")
    rqtProduct_TX = replace(rqtProduct_TX, "<br>", chr(13))
    rqtProduct_TXt = replace(rqtProduct_TX, "&nbsp;", " ")
    rqtProduct_TX = replace(rqtProduct_TX, "''", "'")
   
     
      %>
       <FORM name="form1" onsubmit="javascript: return check_Null();" action="updateSave.asp" method="post">
      
      <input type="hidden" name="id"  value="<%=rsNews("id")%>">
      <table width="556" height="262"  border="1" align=center cellspacing="0"   bordercolorlight="#ECE9E9" bordercolordark="#999999"   class="default">
                        <td width="96" height="31">产品类别:</td>
                        <td width="450" align="left">  &nbsp;&nbsp;&nbsp;&nbsp;<select  name="Cate">
<%
   Set rsCate = conn.Execute("Select * from Type order by Product_ID")
 DO WHILE Not rsCate.EOF
       If CInt(rsNews("Product_ID")) = rsCate("Product_ID") Then
%>
<option value="<%=rsCate("Product_ID")%>" selected><%=rsCate("Product_Type")%></option>
<%  Else  %>
<option value="<%=rsCate("Product_ID")%>"><%=rsCate("Product_Type")%></option>
<%  End If
    rsCate.MoveNext()
  LOOP
%>
</select>
</td>
          </tr>
          
          <tr>
          
            <td width="96" height="31">产品型号:</td>
            
            <td width="450" align="left">&nbsp;&nbsp;&nbsp;&nbsp;<input type="text" size="60" name="Product_XH" class="Inputtxt"  value="<%=rsNews("Product_XH")%>"></td>
          
          </tr>
            <td width="96" height="100">产品图片:</td>
            
            <td align="center">
            <% Response.Write "<a href='download.asp?id=" & rsNews("id") & "' target='_blank'><img src='showimage.asp?id=" & rsNews("id") & "' border=0 width='80' height='60'></a>" %></td>
          
          </tr>
              <tr>
                <td height="156" >产品特性: </td>
                <td align="left">&nbsp;&nbsp;&nbsp;&nbsp;<textarea class="Inputtxt" rows="10" cols="58" name="Product_TX"><%=rqtProduct_TX%></textarea>
                </td>
              </tr>
                <tr>
                <td height="156" >产品简介: </td>
                <td align="left">&nbsp;&nbsp;&nbsp;&nbsp;<textarea class="Inputtxt" rows="10" cols="58" name="Intro"> <%=rqtContent%></textarea>
                </td>
              </tr>
            
                 
          <tr>
          
            <td colspan="2" height="30" align="center"> <input type="submit" value="修改图片" name="submit" class="Inputbtn">
                                 &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;<input type="reset" value=" 重 填 " name="B3" class="Inputbtn">
                                 &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;<input type="button" value=" 返 回 " name="B4" onclick="win_open()" class="Inputbtn"></td>
          
           </tr>
        </table>
        </form>
        <%end if%>

请问这是怎么回事啊？怎么会出错了

有一个字段没有内容

txtcontent = replace(txtcontent, "&nbsp;", " ")
这行有问题，而且好像不是这样用吧？
试试txtcontent = replace(txtcontent, "char(32)", "&nbsp;")
你好像全都用反了＝＿＝