Googlebot DNS Errors
Once in a while, customers who use Google Webmaster Tools tell us they receive a message from Google saying something like “Googlebot encountered 1 errors while attempting to retrieve DNS information for your site”.
If this happens just once, it is almost certainly a “false positive” on the Google end. We run independent nameserver clusters at different data centers run by independent companies. Only one of those servers needs to be working for DNS to succeed, and we’ve never had a simultaneous outage of all of them.
There's a steady background level of people asking the same question on the Internet, too — basically, “Google reported this weird thing once, but everything was working properly on my end”.
Because of this, we're convinced that this is just a glitch on the Google server that was trying to index your site. You can safely just ignore it as long as it only happens once. (But don't ignore it if it keeps happening; that would indicate a real problem that you should contact us about.)