I can now reproduce. e.g. Since you have access to my site - create folder under the top level "years" e.g. 2003 and then look at the properties of the Page settings for that folder.
yes - now I cant reproduce!. I think it has to be something with cached values. It happened after numerous moves and renaming of folders over an extended period of time. I'll keep an eye out if it happens again and the record it.