PHP Login Script not working..

session_start();
ob_start();

//Include the database connection file
include "inc/database.php";

//Check to see if the submit button has been clicked to process data
if(isset($_POST["submitted"]) && $_POST["submitted"] == "yes")
{
    //Variables Assignment
    $fullname = trim(strip_tags($_POST['fullname']));
    $user_email = trim(strip_tags($_POST['email']));
    $phone = trim(strip_tags($_POST['phone']));
    $street = trim(strip_tags($_POST['street']));
    $city = trim(strip_tags($_POST['city']));
    $state = trim(strip_tags($_POST['state']));
    $zipcode = trim(strip_tags($_POST['zipcode']));
    $manufacture = trim(strip_tags($_POST['manufacture']));
    $model_name = trim(strip_tags($_POST['model_name']));
    $year = trim(strip_tags($_POST['year']));
    $vin_number = trim(strip_tags($_POST['vin_number']));
    $mileage = trim(strip_tags($_POST['mileage']));
    $username = trim(strip_tags($_POST['username']));
    $user_password = trim(strip_tags($_POST['passwd']));
    $encrypted_md5_password = md5($user_password);
    $user_access_level = "0";

    $check_for_duplicates = mysql_query("select * from `customer_info` where `fullname` = '".mysql_real_escape_string($fullname)."'");

    //Validate against empty fields
    if($fullname == "" || $user_email == "" || $phone == "" || $street == "" || $city == "" || $state == "" || $zipcode == "" || $manufacture == ""  || $model_name == "" || $year == "" || $vin_number == "" || $mileage == "" || $username == "" || $user_password == "")
    {
        $error = '<br><div class="info">Sorry, all fields are required to create a new account. Thanks.</div><br>';
    }
    elseif(!eregi("^[_a-z0-9-]+(\.[_a-z0-9-]+)*@[a-z0-9-]+(\.[a-z0-9-]+)*(\.[a-z]{2,3})$", $user_email))
    {
        $error = '<br><div class="info">Sorry, Your email address is invalid, please enter a valid email address to proceed. Thanks.</div><br>';
    }
    else if(mysql_num_rows($check_for_duplicates) > 0) //Email address is unique within this system and must not be more than one
    {
        $error = '<br><div class="info">Sorry, the username <b>'.$username.'</b> is already in use. Please enter a different username of your choice to proceed. Thanks.</div><br>';
    }
    else
    {
        if(mysql_query("insert into `customer_info` values('', '".mysql_real_escape_string($fullname)."', '".mysql_real_escape_string($user_email)."', '".mysql_real_escape_string($phone)."', '".mysql_real_escape_string($street)."', '".mysql_real_escape_string($city)."', '".mysql_real_escape_string($state)."', '".mysql_real_escape_string($zipcode)."', '".mysql_real_escape_string($manufacture)."', '".mysql_real_escape_string($model_name)."', '".mysql_real_escape_string($year)."', '".mysql_real_escape_string($vin_number."', '".mysql_real_escape_string($mileage)."', '".mysql_real_escape_string($username)."', '".mysql_real_escape_string($encrypted_md5_password)."', '".mysql_real_escape_string($user_access_level)."', '".mysql_real_escape_string(date('d-m-Y'))."')"))
            $_SESSION["VALID_USER_ID"] = $username;
            $_SESSION["USER_FULLNAME"] = $fullname;
            header("location: index.php");
        }
        else
        {
            $error = '<br><div class="info">Sorry, your account could not be created at the moment. Please try again or contact the site admin to report this error if the problem persist. Thanks.</div><br>';
        }
    }
}
?>