Why does Google Webmaster Tools say my whole site is blocked by robots.txt when I have no robots.txt?

Similar problem occurred to me, and I got the solution following these:

• Step 1: Take a backup of your .htaccess file and then remove it (Don’t worry, on next refresh WordPress will create one for you)
• Step 2: If there’s no robots.txt exists, create one with blank page
• Step 3: Resubmit the sitemap to google webmasters tools
• Step 4: Additionally use “Crawl as google” and add the site again to confirm that things are working fine

Hope within short time your site will be indexed.