on Mac OS QSystemTrayIcon doesn't work properly.
right click can be detected either QSystemTrayIcon::Trigger or QSystemTrayIcon::DoubleClick and never as QSystemTrayIcon::Context.
right click detects as QSystemTrayIcon::DoubleClick when we click second time on the icon regardless of delay of second click.
The context menu shows in any case.
in other words on right click we have two events: some not visible for me which calls context menu and QSystemTrayIcon::Trigger which follows with QSystemTrayIcon::DoubleClick on second click regardless delay.
its defintelly a bug

All tests were done with this my app http://code.google.com/p/qtnote/
I'm not going to invent any workarounds so you can test it at any time. just look at mainwidget.cpp for trayicon activity processing.