Put the touch-screen device, N97-mini, in landscape mode by opening the slide-out keyboard. Launch a Qt application. The space in between the softkeys is active. Pressing that space causes the app to be pushed into the background. It only happens the first time after an application is launched. After bringing the app back to the foreground, the space in between is no longer active.
This is particularly problematic when displaying a vertical scrollbar on the righthand side. Any slip of the finger can easily press the space in between the softkeys and the app appears to vanish (when it is pushed into the background).