A Commenter reported to me recently that sometimes when she visits my blog the Comment name & url fields are already filled in (with other of my Commentors information). I got her to send me some screen snaps and the browser cookie file and sure enough, the cookie is identifying her as someone else. I checked back through my comment logs, and this has happened with other users (who evidently didn't notice it). She can clear the cookie, but it eventually reverts to someone else's details.
Anyone have any idea what's going on here?