Help! Made a boo-boo encrypting credit cards

Hey all - I'm using mcrypt to store credit cards into MySQL. About 90% of them decrypt fine, but about 10% decrypt as nonsense ("b1�\�JEÚU�A���" is a good example). Maybe there is a character that appears in about 10% of my encryptions that's not being encoded properly??? // Encryption is set up at the top of the script: $crypto = mcrypt_module_open('rijndael-256', '', 'ofb', ''); $iv = mcrypt_create_iv(mcrypt_enc_get_iv_size($crypto), MCRYPT_DEV_RANDOM); $ks = mcrypt_enc_get_key_size($crypto); $key = substr(md5('my_funky_term'), 0, $ks); // When the card number is collected by the form, it's encrypted: $cc_number = addslashes($_POST['cc_number']); mcrypt_generic_init($crypto, $key, $iv); $cc_encrypt = mcrypt_generic($crypto, $cc_number); mcrypt_generic_deinit($crypto); // This is written to the database: $query = "update accounts set cc_encrypt='$cc_encrypt', encrypt_iv='$iv', other_fields='$other_stuff' where id='$account_id' limit 1"; $result = mysql_query($query) or die(mysql_error()); Both the cc_encrypt and encrypt_iv fields are tinytext, latin1_swedish_ci, MyISAM, MySQL 5.0.91 In another script, when I retrieve, I first set it up at the top of the script exactly like step #1 above, then retrieve it like this: mcrypt_generic_init($crypto, $key, $row['encrypt_iv']); $cc_number = trim(mdecrypt_generic($crypto, $row['cc_encrypt'])); mcrypt_generic_deinit($crypto); Most of them are good, a few of them are bad. Can anyone see anything I'm doing wrong or a case I'm not covering? Thanks much.