The problem erupted in the verification files of the Google Sitemaps program having google0<unique_string>.html. format has been resolved. This particular file had a bug that stripped out leading zeroes at the time the files were accessed. But, the good news about it is that the team at Google has introduced some useful solutions which would lessen your worries in terms of verification of these files. It is advisable that once you include any site to your account, be it through a sitemap or adding it directly, a proper error and statistics information should be checked timely. This particular feature ensures a complete security of your site, because its detailed staistics can only be seen by the authorized members. But, for those with multiple sites should verify each of them seperately. Verification of the site through Google Sitemaps program is not recommended because it can be directly done through the error information about the sitemaps you've added.
The master minds at Google does a periodical checkup to see whether the verification files of the Google Sitemap program exists on your webserver to make sure that you still are the owner of it. This would overcome the problems which one often come across while doing the verification of such files. I think, the solution to the problem is perfect as nothing better could have been more beneficial. Also make sure that your file names are created as instructed by the Google, for example creating files in GOOGLE11e5844324b7354e.html. format is recommended, so that less problems come your way while performing the file verification.