Hi,
the robots.txt is OK and the sitemap is also OK.
If you have changed the robots.txt recently, check that GWT has the fresh copy.
Also ensure that the the warnings are referred to all links or only a part.
If everything is ok, another possible issue could be not the robots.txt but some other server settings or extensions installed such as Admin Tools that block Google Bot.
Eventually contact me at
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for more details.
Best regards
John Dagelmore