I quit FCPX, dumped the FCPX prefs and restarted the computer. The range selector did not work in my current project even though it was created from scratch in FCPX 10.3.
After experimenting a bit I came to the conclusion that moving forward it should work as long as I am creating a new library with a new event and a new project. The range tool will not work in anything I created prior to reseting the FCPX10.3 preferences, even though those projects were created with FCPX10.3
I would conclude that this is a bug that manifested itself after I upgraded to FCPX10.3. Next time I will reset my prefs after I upgrade. I must have spaced on this one.
Very strange.