In qwidget_s60.cpp QWidget::grabMouse there's this assertion statement that causes some applications to crash in winscw debug emulator:

Q_ASSERT(testAttribute(Qt::WA_WState_Created));

Attached is a simple application to reproduce this situation in the winscw debug emulator.

If the application calls grabMouse() before show() then it shouldn't crash in any build variant. Maybe it should just not do anything, but in any case it must not crash. That's not proper use of assertion statements.