anti-splog 1.0.6.1 includes

blog-suspended.php, lines 37 and 129:
require_once('mu-plugins/anti-splog/recaptchalib.php');

Since anti-splog 1.0.6.1 is only valid in WP 3.1+, which requires a "plugins" install, these lines should each read:
require_once('plugins/anti-splog/includes/recaptchalib.php');