[sammyg2]

Just checked, got an e-mail from AT&T and it said the following, maybe it has something to do with that pop up:

Final notice!
Dear so and so,

We're making improvements to att.net Mail!

On or after June 10, 2013, through July 2013 all users of att.net Mail will be prompted to upgrade their att.net Mail accounts. You'll see some exciting changes in att.net webmail that include a new look and feel that makes att.net webmail even easier to use. Once your account is upgraded, the webmail version you're currently using will no longer be available.




What you can look forward to:
■Faster email
■The latest Mail spam-protection technology and scanning for relevant advertising display
■Easier-to-use design


Important Notes:
■All att.net webmail user accounts will be upgraded regardless of AT&T domain (ex: user@att.net, user@bellsouth.net, user@sbcglobal.net, etc.).
■On the day of the att.net webmail upgrade, you will be able to choose to customize the email scanning settings for your account.
■There is no impact to your email IDs, saved messages, webmail folders, passwords, email client settings, or service, based on this upgrade.
■To learn more about the new att.net Mail visit The new AT&T Yahoo! Webmail - AT&T Email Support


We hope you enjoy the new att.net Mail.


Sincerely,
AT&T Internet Services Customer Care