Mine works fine .
Yahoo in the news lately said starting this week they encrypt all emails for security enhancements. And all searches and messenger stuff to follow. So maybe they hit a snafu on your server or you not accessing with HTTPS or something simple..

Hopefully it will automatically fix it self fast for you... Might help it along by running something like CCleaner to clear your internet cache and restart the computer to make sure a good flush of dns cache.

This has been going on for a couple of months. Sometimes I can access my mail with no problem but sometimes, like tonite when I can see an e-mail in the little preview window that I really would like to read and I cannot get to my mail.

That is why I no longer use yahoo or gmail for my disposable email programs. I made another account with my server that I only use for surfing and registering for a site because I want to join a discussion there. I can close that one if get spammed to much. I route my server's email through windows live mail and never have a problem.