Hi Techbeam,
I just checked on Google and found your site apprearing in the Search Results appropriately which shows that nothing is really wrong with your site.
This Robots.txt file error behaves strangely at times (at least for blogspot domain which I've personally experienced). Since you have your own domain and hence you have access to your Robots.txt file so just go through the help from inside your AdSense account and see if it's alright or not and make necessary changes in required.
I can see the AdSense ads apprearing on your web site. That means you don't really need to be worried about the error. I think the error will disappear soon automatically. The feed migration might have caused this to heppen temporarily.
To be on the safe side ensure that your Robots.txt file is alright and even if the error persists then just write AdSense Support an email.
Please share in case the AdSense Support suggests you something else to do.
Thanks,
Geek
http://geekexplains.blogspot.com