I've actually had this problem pop up on numerous sites in the past 4-weeks in Webmaster Tools, and it seems like a lot of other people are having the same problem. This morning I had a site with a WMT warning of "Severe health issues are found on your site. - Check site health" even though robots contained about what you have going on (It's a WP setup, so there was a disallow on /wp-admin and such).
Originally Posted by cass27
I grabbed a non-functional robots.txt file from another site with no such warnings and it fixed the problem... I think this is a problem Google has right now, not necessarily your site. Here's the commented out code I replaced:
That said, what specifically are you trying to do by fetching as Google? It seems like your site is indexed, so it doesn't look like Google is having problems finding you.