I've got a problem with Google not visiting, and I've raised it both with Support here and on Google's Webmaster forum without finding a resolution. I hope it's not out of place to ask here if anyone has similar problems, or could point me towards a resolution.

Essentially, when I started to investigate why Google stopped visiting my site on 31st August, I went into Google Webmaster Tools; I found that whenever I submit a request to validate my sitemap Google returns a response "Network unreachable: robots.txt unreachable". Moreover, and consistent with this, my raw web logs show that no GET/HEAD request from Google is ever logged in connection with these requests, either success or rejection. [Of course, I understand that I might be dropped from a regular crawl for various reasons, but I don't think this error in response to a specific validation request should occur.]

All the other bots seem to be regularly crawling quite normally, and Google retains my cached pages.. but its bot doesn't seem to be able to see me at all now.

I've checked everything I can.. Support assure me that there is no firewall or blocking filters that could be intercepting Google..

I wonder if anyone can suggest anything I could do?