If your using sitemaps to update Google's crawler, make sure your site is verified; Google is going through a re-verification process.

<quote>
If we don't find the file or tag during this check, the account will no longer show that site as verified, and you'll no longer have access to diagnostics and statistics
</quote>

Link:
http://sitemaps.blogspot.com/2006/08/time-to-verify.html

That's why their bot try every 5 hours to access to this file... deleted.
Thanks NateDawg
Thanks Vanessa...