Start Menu keypress inconsistent

once ROS has booted to the desktop,

• Pressing the start button key on the keyboard would trigger no response from the desktop.

• Pressing it a 2nd time would bring up the start menu.

• However, after closing the start menu by clicking somewhere else, entering any key other than the start button key on your keyboard would bring up the start menu again.

• 3rd and subsequent start button key presses bring up the start menu and do not cause above strange behaviour.

Confirmed in trunk by myself and amine48rz.