ok not the system.gui.createPopupMenu() but the menu.show.
menu.show(event) does not show the menu.
menu.show() does show the menu but now there is no event to pass to the menu functions so they throw exceptions.
not often my posts go ignored 
Ahh, the lovey sound of crickets reminds me of a warm summer evening. Much better then what it is outside my office right now.
fixed in 7.3.2 beta 5 maybe?
Hmm, you say that 7.3.1 breaks this function, but compared to what? Nothing with that function has changed in a long time.
Perhaps you’re running it on a different machine, and it acts differently?
[tt]menu.show(event)[/tt] will only show the popup if MouseEvent.isPopupTrigger() returns true. When this returns true is system-dependent: macs are different than PCs for this. For proper coverage you’d want to make sure and call this from both [tt]mousePressed[/tt] and [tt]mouseReleased[/tt].
If you want to avoid this platform-dependent mess and just pop it up when you damn well please, call [tt]menu.show(event, x, y)[/tt] directly. Not [tt]menu.show()[/tt].
If this was all review and you have a genuine issue, you’ll have to show me how to reproduce it, because I can’t.
I would accept your challenge. 
but then I would have to show you my crappy code that caused my problem 
I take that to mean you got it figured out?
Yep, combination of OTIP and RTFM.
To summarize: PEBKAC