So, when you install Muse it asks for an Adobe ID. That info is stored with the program.
When I go to publish a site for the first time ever, it comes up with "Upgrade To Adobe ID" dialog box.
My Adobe ID (email) shows in there. I enter my Adobe ID password and can't get past the dialog since it tells me the password is correct.
I know it's correct. The thing that is a bit confusing is the dialog makes it sound like I enter a "BC password" — when I never created an account there? Is the password my Adobe ID password?
The dialog you describe only comes up if there's already an account on Business Catalyst that's using the same e-mail address as your Adobe ID (and the Business Catalyst credentials have not yet been converted to be an Adobe ID).
If you go to businesscatalyst.com and attempt to login with your e-mail address you should be able to use the "Forgot Password" mechanism to set a new password that you could then provide in this screen in Muse.