Why does this snippet in a blog post make WordPress crash?

Question

Ok, this is seriously weird and I have no clue what's going on here. I am using WordPress 3.0.1, I create a new blog post, give it a title, paste the following code into the blog post and hits Save Draft.

<code lang="php">
// Init curl
$request = curl_init();

// Set request options
curl_setopt_array($request, array
(
    CURLOPT_URL => 'https://www.sandbox.paypal.com/cgi-bin/webscr',
    CURLOPT_POST => TRUE,
    CURLOPT_POSTFIELDS => http_build_query(array
        (
            'cmd' => '_notify-synch',
            'tx' => $_GET['tx'],
            'at' => $your_pdt_identity_token,
        )),
    CURLOPT_RETURNTRANSFER => TRUE,
    CURLOPT_HEADER => FALSE,
    CURLOPT_SSL_VERIFYPEER => TRUE,
    CURLOPT_CAINFO => 'cacert.pem',
));

// Execute and get the response and status code
$response = curl_exec($request);
$status   = curl_getinfo($request, CURLINFO_HTTP_CODE);

// Close
curl_close($request);
</code>

Just a code example in my head, but seems like WordPress thinks otherwise, cause when I hit Save Draft, Preview or Publish all I get is a blank page with the following text:

Service Temporarily Unavailable

The server is temporarily unable to service your request due to maintenance downtime or capacity problems. Please try again later.

What in the world is going on here??