I have been using google sitemaps for months now - with no problems.
However, today it asked me to verify my site again which I had already done using a HTML file. When I click "verify" again, it says:
We encountered an error looking up your site's domain name.
We tried to access your verification file, but were unable to access your domain due to a DNS error. This could be because your server is down, or there is an issue with the DNS routing to your domain. Make sure that your domain is resolving correctly and try again.
Hi: I suspect nothing wrong with your server of DNS servers. This happened to me a few times. Log out of your Google email account - use the link on the upper right hand corner of the Webmaster first screen. Then log back in and you will suddenly be 'verified'. Weird but it works.
I'm glad to see this is not isolated to myself - I just got off the phone with my datacenter manager wondering if it was an issue on our end and we were about to go nuts trying to figure it out... i can take a nice deep breath now...