sitemap.xml error in WebMaster Tools: Correct Way to Submit to Search Engines (particularly Google)

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Hy,

Just launched a site, added it to Google Webmaster tools. Submitted the XML sitemap generated by concrete5. However in Web Master Tool shows Issue:"Url blocked by robots.txt."

Issue Description: "Sitemap contains urls which are blocked by robots.txt"

How to correct this error ?

I believe the error is due to the theme folder entry in robots.txt. If that entry/block is intentional by concrete5 team, then what is the correct way to submit a new site to Google for indexing or have it show up in WebMaster Tools.