We've seen routers and other devices that reply to pings on several IPs even though no devices or computers are actually connected to them. We're not sure why this is, but it may be security related, in the same way honeypot networks contain virtual machines that respond like a computer to allow you to easily detect hackers without damage to your real systems. Almost always, even though the addresses return a ping, these IPs will also have an expired TTL (Time-to-Live). In the latest version we've added a feature to help ignore these types of IP addresses.
Please let us know if we can be of any further assistance and we hope you enjoy version 2 when released.