Opus shouldn't be elevated or you'll run into problems making Opus react to and interact with normal unelevated apps. (Same as Explorer shouldn't be run elevated.) Use the UAC support in Opus to do work that requires elevation.
I don't know much about Calibre but I'm surprised if e-book software that's still being updated in 2015 needs to run elevated?
[quote]and I am able to Drag & Drop to all programs I need, other than Calibre, which is also elevated.
Curiously, I can drag a book from Calibre to my actual desktop, but not directly into the Desktop folder in DOpus - which is what I'd rather do.
Is this possible? (I have tested, and can drag and drop into the Explorer Window.)[/quote]
First line is about dragging to Calibre. The others are about dragging from Calibre.
Are you able to drag from Explorer to Calibre?