Product and Version: FM17
OS and version: latest Mac OS
Hardware: 2014 MacBook Pro, retina, and Apple Cinema display
Description: FM17 strips the ability to activate an object for arrow key nudging, unless that object was directly touched with a mouse click immediately prior. This "locked-out" status also occurs after changing an object's theme style.
In FM16, I frequently made small adjustments to the location of a layout object by selecting the object in the object picker, clicking on the main edit-layout window, to activate the window and object, and then used my arrow keys to nudge the object 1 pixel at a time, in any direction.
How to replicate: Pick an object using the object picker embedded in the window and/or change an active object's theme style. Click somewhere outside of the object picker or inspector to bring the focus to main window rather than the picker or inspector. Trying to move the object, which should still be active, with the arrow keys, will, at best, bring you back to the picker or inspector and move your selection up or down from your previously active location.
Workaround: Hide objects in front, or do complicated selection/de-selection mousing technique to select any objects in the layout window that aren't on top. Or, type in new coordinates in the inspector and don't use arrow keys.