I am using Magento for my site.
Recently I blocked my website for the U.S. using the PHP Geo IP Location country database.
This means that when people visit from the U.S., the site will show just a restricted access message.
But the next day when I logged into my Webmaster Tools account, I see errors for 300 pages.
500 errors for the links, however the pages are working for me.
Here is the error reported by Google:
http://example.com/: Increase in server errors May 4, 2014 Google detected a significant increase in the number of URLs we could not access. It is likely that your server had an internal error or was busy when attempting to process these requests.