The above error message appears at the bottom of the meta box. I can manually delete post revisions but it does not seem to work automatically. For example, I have post revisions set to 2 but I had 10 revisions on my last post. I was able to delete all but the current and last one. I am running twenty-eleven theme. I saw a prior post regarding this issue, a year old, but I could not make any sense out of the resolution.