membership payment gateway changes fail

I get this message when trying to save changes on the PayPal Express Payment Gateway page:

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Forbidden

You don't have permission to access /~rideadve/wp-admin/admin.php on this server.

Additionally, a 404 Not Found error was encountered while trying to use an ErrorDocument to handle the request.
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I have tried CHMODDING via FileZilla on teh admin.php to 777 but still no luck.

Anyone have any ideas on this error?

@PaddyJames