Why my MySQL some table vlaue have '', this show up as '�' while I am press edit

Hi all,

I am using ZC 1.5.1, and it upgrade from 1.3.2 then 1.3.7 then 1.3.9h
While on 1.3.9h I am also run the Dr.Byte latin-1 convert to UTF8, running long time and look like work well..

And I am always using phpmyadmin as the backup and restore tools by my VPS cPanel build in...

But today I open some backup MySQL tables, see it value have some funny value in it ...

DROP TABLE IF EXISTS `address_book`;
CREATE TABLE IF NOT EXISTS `address_book` (
  `address_book_id` int(11) NOT NULL AUTO_INCREMENT,
  `customers_id` int(11) NOT NULL DEFAULT '0',
  `entry_gender` char(1) NOT NULL,
  `entry_company` varchar(32) DEFAULT NULL,
  `entry_firstname` varchar(32) NOT NULL,
  `entry_lastname` varchar(32) NOT NULL,
  `entry_street_address` varchar(64) NOT NULL,
  `entry_suburb` varchar(32) DEFAULT NULL,
  `entry_postcode` varchar(10) NOT NULL,
  `entry_city` varchar(32) NOT NULL,
  `entry_state` varchar(32) DEFAULT NULL,
  `entry_country_id` int(11) NOT NULL DEFAULT '0',
  `entry_zone_id` int(11) NOT NULL DEFAULT '0',
  PRIMARY KEY (`address_book_id`),
  KEY `idx_address_book_customers_id_zen` (`customers_id`)
) ENGINE=MyISAM  DEFAULT CHARSET=utf8 AUTO_INCREMENT=65244 ;


INSERT INTO `address_book` (`address_book_id`, `customers_id`, `entry_gender`, `entry_company`, `entry_firstname`, `entry_lastname`, `entry_street_address`, `entry_suburb`, `entry_postcode`, `entry_city`, `entry_state`, `entry_country_id`, `entry_zone_id`) VALUES
(16, 16, 'm', NULL, 'cplam', 'LAM', '15e, estate, ssp', '', '00000', 'hkg', 'a', 96, 0),
(51327, 36345, '\0', 'A', 'car', 'si', '24 CT', '', '32', 'DELTONA', '', 223, 18),
(51328, 36346, '\0', NULL, 'ron', 'ab', '16 fond', '', 'h9h3x7', 'pierrefonds', '', 38, 76),

As on above example, where table column 16 is general value, but ....
51327, and 51328
on the 'entry_gender' column it have a value '\0'
who using ZC also know this on this will be m or f only, not other value ....
if I using phpmyadmin press the edit, this value will show up as �

Why have this value on the MySQL table?
Above just one of my tables have this '\0', other table such as currencies I am also experience this ...

Can anyone tell me why? Or which part is broke/wrong to make this?

Thank you.