Debug build of Qt sometimes aborts with ASSERT

When building against the debug version of Qt 4.6.2, my application sometimes aborts with:

ASSERT: "!(*watched)" in file widgets/qmenu.cpp, line 997

I am not able to accurately reproduce the abort; it seems to happen at random when navigating the menus of my application. But someone on the Qt mailing list mentioned:

"I have also seen this with several version of Qt including 4.7 beta 1. The way I trigger it is to open a non-modal dialog from a menu, then go back to the menu and move the mouse over the menu items. I do not understand what's wrong, but it goes away if I use Qt::QueuedConnection in the connects for the menu."