Wow, this is frustrating, I responded to these comments several days ago but they didn't post, apparently. d_stranz--I actually did initialize QMainWindow in the MainWindow constructor, I just forgot to put that in the snippet. (My firewall at work blocks QtCentre ?!?! so I have to reply from home.) Passing window flags from the constructor didn't help. wysota--I had everything together in that snippet just to show that I had tried all those different things, I tried out showFullScreen(), manual settings independently as well.

I'll try to keep update() and showFullScreen() out of the constructor, and see if that helps. Thank you both, so far--

Matt