With AdBlock Plus is enabled, go to:
https://disneyworld.disney.go.com
Click on "Sign In" on the top toolbar. This takes you to a login page. Login successfully. Just takes you right back out to the home page as if you never attempted login, where there is still an option to "Sign In" on the top toolbar, instead of your name. (note that if you type your password incorrectly you get an error, so this is not an issue with forgetting credentials)
Spent couple hours with Disney's worthless customer service on this issue. Then it occurred to me just to try disabling Adblock Plus, and to my surprise, immediately corrected the issue. Now when I login, my name appears on top and I am able to retrieve my information from the menu options.