I think this should work.

sp_change_users_login 'dbo', 'dbo', 'Update_one'

The issue at least to me - was my dbo was mapped to the wrong user. And that is a no-go.

You will...

Paul, thanks - all these mods you made makes sense. I haven't had a recurrence in a while, but now that I said it, you know what's coming.

But atleast I...

Did you find a resolution for this issue? Did MS help?

We are having a pretty much similar situation, and didn't want to reinvent the wheel..