I test your example of sort on some content object of my project and it's working : the greater vote is in first. Strange ?
If you look here http://ez.no/doc/ez_publish/technical_manual/4_0/reference/modules/content/fetch_functions/list integer datatype is supported with sorting on the attribute level.
if u are updating the attribute vote by sql, u have to update the field sort_key_int of the table ezcontentobject_attribute, it's something like this:
$l_STR_Requete = "UPDATE ezcontentobject_attribute
SET data_int = \"".$l_INT_Nb."\", sort_key_int = \"".$l_INT_Nb."\"
WHERE version = \"".$l_TAB_Resul[0]['version']."\" AND id =\"".$l_TAB_Resul[0]['id']."\" ;";
