I was able to solve the issue.
I used an older version of mstsc.exe from 2007. I created the RDP file using this version, saving the correct parameters, such as screen resolution and security warnings.
To use the new RDP, I made a shortcut on the Desktop to run c:\temp\mstsc.exe c:\temp\profile.rpd.
This cleared the problem of the screen not filling in correctly.
Until a Microsoft Update addresses the problem, this is a workaround.