Sudden drop in keyword ranking

[tanveer1]

Since last Friday (09/28/12) all of my keyword ranking is gone. I checked the webmaster and found, among the others, one error "access denied" "1 error found" "server requires login or is blocking googlebot" Im trying to see if this thing has to do with sudden drop of ranking? I have other sites on the webmaster and none of them is showing this type of error. Help will be appreciated.

When I check individual urls they are there (indexed).

[SEOAndy]

The first thing that springs to mind is your robots.txt file. Is robots.txt blocking something it shouldnt be? it sounds like it might be if Google literally can't get onto your site to crawl it.

When was the last time your individual URLs were indexed?

[tanveer1]

One thing, for sure, I know I didnt change any robot.txt. It has always been like this:

User-agent: *
Allow: /

Is this the correct format.

[tanveer1]

One thing, for sure, I know I didnt change any robot.txt. It has always been like this:

User-agent: *
Allow: /

Is this the correct format.

[SEOAndy]

Yeah that is correct.

You haven't changed any code on your website have you? meta robots tag or anything like that?