Yea, that started for me today too, though Cimics reported it earlier. The IP that is listed is not the IP that my site is located on. A couple of days ago some spammer came in and posted something which I deleted right away. My hunch is that it just so happens that right then Google scanned the page. So, now we all know how to break a site, don't we? Just go in, anywhere, to any site, and post a single bad link. That'll bring it crashing down to its knees. I half suspect this is an evil google plot to insert itself more insidiously on the Internet. In order to get this alert to go away I had to go and sign up for their stupid webmasters tool thing, add a site, and request a review. This kind of thing disgusts me.
At any rate, I requested the review. Alternatively, you can change your security settings so that you don't receive warnings.