It is working fine for me as well. Are you using a bookmark? If so try going to yahoo and then clicking the mail link from there
My, apparently, went down last Friday. Strangely, I had to wipe all cookies on my browser to gain access. I've never had to do that before.
No problem to me though. Try posting on http://forums.yahoofanclub.com we might give a good reply. umm... strange.