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I believe this is the 4th time this has happened with enom in the past 2 years. Kind of makes me skiddish about using enom's name servers. And no official word from enom... so we have no idea if this was a bad root update or some kind of dns poisoning.
I do believe that Google maintains their DNS cache for 3 days, so it's possible that Google could find the sites even though first time visitors could not. (Sites would still be reachable by IP address.) My main site which I monitor more closely than the others didn't experience any reduction in crawling by the G-bot and this is the only explaination I can think of.