What kind of local problem or network problems could cause a servfail response from the authoritative ns?
I'm beginning to think this is a DNSSEC related problem, I'll ask on the pdns-users list. I see it's asking for a DS record on login.authorize.net.cdn.cloudflare.net when the nearest one appears to be at cloudflare.net, so for some reason that's not being applied all the way down.
