I've had an email today saying that the secondary nameserver IP for FoolDNS changed a couple of weeks ago.
There's some information here (thanks, google translate!) http://www.fooldns.com/2012/11/fooldns-nuovo-indirizzo-per-dns2-a-causa-di-problemi-tecnici/
In the past I would just update the IP addresses in the app and then push out a quick minor release update. However, in the recent changes for version 2 we moved the IP addresses into a database in preparation for future updates that will allow us to better manipulate the IP's and the DNS list.
Consequently I'm going to test the changes to make sure it won't break any running devices first before pushing out the update, which will be in a couple of days.
In the meantime, if you use FoolDNS you can use the following settings as custom DNS servers: