Help: The page you requested is NOT AVAILABLE; A general error has occurred

background:

1. version: 1.3.9h; host: ixwebhosting

2. two payment methods tested: COD (cash on delivery) and Paypal Express Checkout

3. include/configure.php and admin/include/configure.php: ssl=false

4. zencart configurattion: check ssl session=false

5. choose product -> shipment method -> payment method -> confirm payment, before i click the "confirm" button, everything is ok, and now the url is ........checkout_confirm, click the "confirm" button, customer(me) and the store owner(me) has the order email immediately, the url is ...........checkout_process, after about 3-5 seconds, i read "The page you requested is NOT AVAILABLE; A general error has occurred ". and now if i changed the url to "...........checkout_success", it showed"Thank You! We Appreciate your Business!
   Your Order Number is: 20
   Thank you for your shopping with us! your order is proceeding now!"

6. then i changed the payment to Paypal express checkout and tried again, the same error occurred, and i checked the Paypal payment history, it showed i have already paid/received the money.

thank you in advance.

1. i checked /cache/ , no log files about this issue.
2. enable_error_logging.php, @ini_set('display_errors', 1); // do not output errors to screen/browser/client
   and i tried again, same again, "The page you requested is NOT AVAILABLE; A general error has occurred ".

pranovo:

The page you requested is NOT AVAILABLE; A general error has occurred
There's no such message anywhere in Zen Cart code.

So, the message itself is being triggered by something external.

You'll need to investigate further to find out what's triggering that message. Maybe your hosting company's server logs might help?

Maybe you've added plugins that change normal Zen Cart operation, and something there is malfunctioning?