Firstly, kudos for actually providing real domains. It makes the diagnosis much easier.
Running http://squish.net/dnscheck over the record in question says:
50.0% of queries will end in failure at 126.96.36.199 (ns1.projectinprogress.com) - returned SERVFAIL code
50.0% of queries will end in failure at 188.8.131.52 (ns2.projectinprogress.com) - returned SERVFAIL code
I'm going to take a wild stab in the dark and guess that you've put both your DNS servers on the one machine, and now you've just learnt why that is a phenomenally bad idea. There are whole RFCs dedicated to why that is a bad idea.
As to why your DNS server has suddenly decided to fail all queries, that's beyond me because you haven't provided any diagnostically relevant information on that aspect of things. Take a stab at it yourself, but if you can't figure it out you'll need to provide your DNS server software, version, and relevant-looking log messages (but probably ask a separate question as it'll get too confusing in this one).