Hi. I'm a happy long time mac user. Never had a problem, never a serious trouble system. But a couple of weeks ago it happened something disturbing: I transferred some movies and various documents to an external HDD, I worked as usually, with the usual applications, lastly I logout the session. Well, just one second after the login screen appeared, I see my two user accounts (mine and my wife's) suddenly disappear! In place of them, there's one new account named "other ". It is inaccessible due the unknown password. At last I had to use the Snow Leopard install cd to recreate a root user, so I was able to log-in and recreate my user accounts and associate them with old user folders, still intact. At last all the thing seemed to come back at the right place, no file or setting lost. Anyway, to be prudent, I formatted and reinstalled Snow Leopard, put my documents and apps and upgraded the OS. After few days, I log-out from my session and tadaa, my user account is lost again! On the login screen I see only the damned "Other " user account! I googled and consulted several forums for an answer, but nothing. Is there anybody who can tell me more about this weird behavior? Many thanks.