Found out this week that VaultPress needs a little help to communicate with a WordPress site behind CloudFlare.
And I do mean a little help.

Brian at VaultPress showed my that all it takes is adding one line to your wp-config.php file to make everything work.

/**
 * For compatibility with CloudFlare
 */
  if ( !empty( $_SERVER['HTTP_X_FORWARDED_FOR'] ) )
    $_SERVER['REMOTE_ADDR'] = $_SERVER['HTTP_X_FORWARDED_FOR'];

CloudFlare and VaultPress now play quite well together. We have noticed many of our pages are loading a good deal faster, and domain name resolution happens in a flash.