Same problem here, and also started on the same date, 10/18/2011. I have tried 3 different computers, 3 different browsers and nothing works. I have switched back to Yahoo Classic, but it still does not work. The only difference being that when I try to attach a file I get a web page that just says "Server Hangup". In the "new" Yahoo Mail you get no indication of error. It just does nothing. I have another, less used, Yahoo account and everything works fine there. I'm guessing that this problem is isolated to a group of user accounts, probably all housed on the same server or set of servers. Just a guess. Getting help from Yahoo via the web is impossible. We need to find a way to notify them of this issue. ADDITIONAL INFO: As of this morning, 10/20/2011 attachments seem to be working again. I can upload and download e-mail attachments so Yahoo must have found the issue. If you are still having problems I would say be patient as it seems that they are working on it.