Tell me more about your setup.  Is your Nanobeam receiving an IP address dynamically from the router or is it static? The first thing I do when I setup a Ubiquiti radio is change the default IP to something else.  Also, as has been mentioned, I have my DHCP server set to only handout addresses that are in a specific range above .100.  All my static IPs are in the 0-99 range.  Lastly, for now, if a radio sees a power surge they will often reset to the factory IP address.