Other PAYPAL 303 and Rifle error

What causes a 303 error when I make a call on my website to paypal?

Here is a snapshot of the message:
http://www.arguemax.com/images/problems/5-21-2014/Capture_02.PNG

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http://youtu.be/728GYPBLYhU

A look at the php code tracks the problem down to this function and "failed with code: {$result[0]} - {$result[1]}" is where the message "failed with code: 303 - rifle" comes from. Can anyone suggest how I can debug this?

Code:

	private function process_request($data)
	{
		global $config;

		$request = new HTTPRequest($this->host, $this->endpoint, 'POST', $config['pp_paypal_secure']);
		$data['USER']		= $config['pp_paypal'.($config['pp_paypal_use_sandbox'] ? '_sandbox_' : '_').'API_username'];
		$data['PWD']		= $config['pp_paypal'.($config['pp_paypal_use_sandbox'] ? '_sandbox_' : '_').'API_password'];
		$data['SIGNATURE']	= $config['pp_paypal'.($config['pp_paypal_use_sandbox'] ? '_sandbox_' : '_').'API_signature'];

		$temp = http_build_query($data);
		$result = $request->connect($temp);
		$return=false;
		if (is_array($result))
		{
			$this->last_error = "failed with code: {$result[0]} - {$result[1]}";
		}
		elseif ($result<400)
		{
	  		$response = $request->get_content();

			parse_str($response, $this->EC_data);
//			$this->write_results($this->paypal_vars['METHOD'] . ' process request returned = ' . $this->EC_data['ACK']);
			if ($this->EC_data['ACK'] == 'Success')
			{
				$return=true;
			}
			else
			{
				$this->last_error = 'Failed Validation';
			}
		}
		else
		{
			$this->last_error = "failed with code: {$result}";
		}
		return $return;
	}