Windows Security Window Empty - No User or Password Fields

I had a situation where adding an Office 365 account to Outlook 2016 would produce the following window when asking for the user credentials:
windows security empty window
i.e. No entry fields for the login or password - huh?!?!?!
After weeks of googling, letting it sit for a while, more googling, letting it sit for a while, even more googling I stumbled upon a Microsoft Technet forum page that hinted at the C:\ProgramData\Microsoft\User Account Pictures\user.bmp file not being to Windows liking. This rang a bell since as part of my setting up the customers Windows 7 DVD image for install I had made a custom user tile.
Once I had opened the user.bmp in MS Paint and resaved (as a 24-bit Windows Bitmap File) all was good! I retried the Outlook 2016 Office 365 and BOOM! the User Tile, Login Name and Password all displayed, waiting for entry.