After several days of search with no progress, we stumbled upon a QT bug:
https://bugreports.qt.io/browse/QTBUG-28766
With QT5, in addition to expected QT libraries, msvcr100.dll, and msvcp100.dll; it turns out that you have to ship your application with:
platforms/qminimal.dll
platforms/qwindows.dll
as well. Which is found in your local QT5 library install @: \Qt5.0.0\5.0.0\msvc2010\plugins\platforms
I searched everywhere, and I was unable to find this info in their documentation.