1) The line you removed:
$WA_where_fieldValuesStr = "".$_SESSION['VisitorID'] ."";
needs to be there, you should not remove that line.
2) if it still does not work, wha thappens if you change:
$MM_editCmd = mysql_query($WA_Sql, $WA_connection) or die(mysql_error());
to:
die($WA_Sql);
$MM_editCmd = mysql_query($WA_Sql, $WA_connection) or die(mysql_error());