Debes de quitarle las comillas a los parámetros de la consulta, asi debe de quedar:
Código C#:
Ver originalquery = "UPDATE tblowners "+
"SET " +
"NAME = @NAME, " +
"TELEPHONE = @TELEPHONE, " +
"CELLPHONE = @CELLPHONE, " +
"ADDRESS = @ADDRESS, " +
"MAIL = @MAIL" +
"WHERE ID_OWNER = @ID_OWNER ";
Saludos