KDE4/Qt4 based apps' menus don't appear on second monitor in WindowMaker

So, I’m running WindowMaker on a two-monitor, one-screen setup. Whenever I start a KDE4/Qt4-based application and drag its window to my secondary monitor, and click on any of its menus, they either fail to appear or show somewhere in the left corner or left-center part of my primary monitor instead, completely detached from its window.

For the heck of it, I have tried to reproduce this problem with a few other window managers. KWin, Openbox, Fluxbox, E16, IceWM, FVWM, heck, even the ancient TWM, which may not even support multiple monitors for all I know. Of all of those, only IceWM had the same exact problem.

Why would WindowMaker and IceWM have an issue with KDE and Qt menus in a multimonitor setup, and why would any other type of application (Gtk2/3, KDE3/Qt3 [yes, I got the old Amarok and ran it just for this] or Qt5-based, Firefox, Chromium, LibreOffice) work just fine in those same environments? Any why just under those WMs and not, say, KWin or Openbox?

My setup:
openSUSE 13.2 (kernel 3.16.7-7-desktop)
KDE 4.14.5
Qt 4.8.6
WindowMaker 0.95.6
NVIDIA GeForce 9600gt driver 340.76-36.1