What character set does that data column use? You may need to ensure that your script is in agreement with the MySQL server as to what character set to use (example assumes UTF-8 character set):
mysql_query("SET NAMES 'utf8'");
mysql_query("SET CHARACTER SET utf8");
// rest of database interaction . . .
You also may want to try to get your web pages and forms to also be in the same character set via a Content-Type header as well as an accept-charset setting in any form tags:
<?php
header('Content-Type: text/html; charset=UTF-8');
?><!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd">
<html lang='en'>
<head>
<meta http-equiv='Content-Type' content='text/html; charset=UTF-8'>
<title>Untitled</title>
</head>
<body>
<form action="" method="post" accept-charset="UTF-8">
</form>
</body>
</html>