This ussually happens if gpc_magic_quotes is turned on in he php.ini file.
the gpc_magic_quotes option is a deprecated setting and not be enabled in the php.ini file.
if your host will not turn off gpc_magic_quotes, you can try adding the following code to line 1:
<?php
if($_SERVER['REQUEST_METHOD'] == "POST") {
foreach($_POST as $k => $v) {
$_POST[$k] = stripslashes($v);
}
}
?>