I got this message in Google Webmaster Tools with a DNS error. My robots.txt is good and there is no redirect when I go to the site. Any ideas?
Maybe your web host experienced a downtime during the time Google tried to index your site. Just wait for a few days for the errors to disappear.
I suggest trying to re-crawl manually with GWT and see if the error keeps happening. What SEO Power said is right, they probably wanted to access the site when it was down.