New Post: Is it possible to use a variable to store the value pairs for a SPServices.UpdateListItems call?

In my opinion one of your variables contains illegal XML characters.
The simplest solution would be to wrap such variables into CDATA. look here: http://www.w3schools.com/xml/xml_cdata.asp
I personally have a cdata function in my JavaScript library, and use it as follows:

function cdata(str) {
   if (str && str != ""){
        return = "<![CDATA[" + str + "]]>";
    }
    else
       return "";
}   

["Description_x0020_of_x0020_Dutie", cdata($descDuties.val())]

Regards
Michal