mysql - C# MySqlReader - Unrecognized GUID format -

i'm reading several tables using mysqlreader , works fine until reach table throws exception saying unrecognized guid format. why's happening?

here's script creating table:

drop table if exists `mcdb`.`reactor_data`; create table  `mcdb`.`reactor_data` (   `reactorid` int(11) not null default '0',   `max_states` tinyint(3) not null,   `link` int(11) not null default '0',   `flags` set('activate_by_touch','remove_in_fieldset') not null default '',   primary key (`reactorid`) ) engine=innodb default charset=latin1 comment='defines reactor information.'; 

here reading code:

foreach (var datum in new datums("reactor_data").populate())         {  ...  internal void populateinternal(string fields, string constraints)         {             this.values = new list<datum>();              string query = string.format("select {0} {1}{2}", fields == null ? "*" : database.correctfields(fields), this.table, constraints != null ? " " + constraints : string.empty);              using (mysqldatareader reader = mysqlhelper.executereader(database.connectionstring, query))             {                 while (reader.read())                 {                     dictionary<string, object> dictionary = new dictionary<string, object>();                      (int = 0; < reader.fieldcount; i++)                     {                         dictionary.add(reader.getname(i), reader.getvalue(i));                     }                      this.values.add(new datum(this.table, dictionary));                 }             }         }