When Outlook is running, it will periodically "talk" to Microsoft to validate my account, and always fails validation. By that I mean I can go into my Account activity see that each time Outlook makes a call to "roaming.officeapps.live.com" (seen with Fiddler), and directly correlates with the number of "Incorrect password entered" (with the "Browser/app" listed as "Internet Explorer") events. Eventually this locks my account.
My Microsoft account password is up-to-date in Windows 8.1 (Your Account Settings), Office (2013 Pro), and everywhere else. Even in Outlook's Office Account section, I made sure the password is current. Again, this only happens when Outlook is open, and will repeat about once per minute. This happens even when I run Outlook in Safe Mode.
I'm assuming I'm missing a place where I have to update my credentials, but I don't know where they would be. I think I've looked everywhere.