Are you sure that Google can't crawl your site? It's very normal for Google Webmaster Tools to give you errors with the robots.txt file. This is because the robots.txt is an optional file. It's a file that you can put in your root directory to specify which search engine spiders you want to allow/disallow to your site, or from specific directories on your site. If there is no robots.txt file in your root directory, search engines will simply assume that there are no restrictions, and proceed as normal.
Since I can't see your site to know for sure, you could try checking to see if you have a robots.txt file, as well as ensuring that there's nothing in it that could be blocking your site. If you are not finding anything there, then I wouldn't worry about it. But if you do know for a fact that there's something going on, then maybe get back to us and we could try looking into it further. You could maybe even PM your domain.