registration WAS working, now says Unable to verify POST var

[webnola]

Ok, so I've been scouring this forum for a few hours and can't seem to solve my problem.

The registration WAS working, now it's spitting out "Unable to verify POST vars" and killing the signup.

I have not made any changes to the server that would have caused this. IPN and PDT are configured correctly, and I've gone over the steps here multiple times. Everything checks out.

Server:

PHP: 5.2
System: Linux
Apache: 2
Curl: enabled | libcurl/7.18.2 GnuTLS/2.4.2 zlib/1.2.3.3 libidn/1.15
Fopen: On
Sandbox: Off
Logging: Tried both on and off, no dice

I have tried the three files:
curl-test-http-google.php (doesn't work)
curl-test-https-paypal.php (doesn't work)
fopen-test-https-paypal.php (works)

My next step is to locate and change php.ini to disable curl, but I'm curious what would make me have to do that? Like I said, I haven't changed anything on the server to make this happen. So it basically worked, and now I'm going to have to disable curl to make it work again? That makes no sense....

Wanna know something else weird? If I create a new php file with the following curl script, it works:

<?php
// FIND BOOKS ON PHP AND MYSQL ON AMAZON
$url = "http://www.amazon.com/exec/obidos/search-handle-form/002-5640957-2809605";
$ch = curl_init(); // initialize curl handle
curl_setopt($ch, CURLOPT_URL,$url); // set url to post to
curl_setopt($ch, CURLOPT_FAILONERROR, 1);
curl_setopt($ch, CURLOPT_FOLLOWLOCATION, 1);// allow redirects
curl_setopt($ch, CURLOPT_RETURNTRANSFER,1); // return into a variable
curl_setopt($ch, CURLOPT_TIMEOUT, 3); // times out after 4s
curl_setopt($ch, CURLOPT_POST, 1); // set POST method
curl_setopt($ch, CURLOPT_POSTFIELDS, "url=index%3Dbooks&field-keywords=PHP+MYSQL"); // add POST fields
$result = curl_exec($ch); // run the whole process
curl_close($ch);
echo $result;
?>

Can anyone help?