In the last two days, I’ve run into a hang/problem starting the simulator on my Mac (Sierra).
Corona Simulator version 2017.3184 (2017.12.8) . (@Rob…be sure to see penultimate paragraph, thanks.)
The problem: simulator hangs, and after awhile (30 seconds?) it displays a red error message in
the console window:
system.deletePreference() function is not supported. Use the system.deletePreferences() function
and a pop-up that offers a choice between continuing or always continuing (IIRC).
Like the OP (see below), nothing in my code is using system.deletePreference.
“Nothing changed” in the last week, AFAIK, so this is really odd. The Mac was rebooted 4 days ago,
and that’s probably when this started.
(I try not to install Apple patches to macOS, and auto-update is off … I’m postponing doing some
more analysis of the impact of Spectre bug patches 
(I just noticed the problem doesn’t always show up at simulator start.)
Why / How do I resolve this?
Although this question was asked a few months ago, it was in the wrong forum, and Rob said he’d
move it to the correct (albeit unnamed) forum. However, I could not find it via either a “Search Forums”
or via a google search of the site. The original thread is at:
https://forums.coronalabs.com/topic/72354-systemdeletepreference-function-error/
I did search through the Corona /Library files, and there are no instances of “system.deletePreference”
other than in two example files. There are about 5 instances in binary files, but I can’t tell if they’re
being used or not, or in what context the string appears.
thanks,
Stan