Binary package hint: gnome-panel
This is a big problem for new users working on laptops. Essentially due to the way the trackpad works the top panel will often be flipped to the left, right or side of the screen, with the user being unware of how to place the panel back up the top. After googling extensively and searching through all the gnome options there seems no option available to lock the top and bottom panels into place; this seem inconsistent with the general interface as it is very easy to lock in place items that are the panel itself. I would propose that the panels be locked by default and that an option to unlock the panels be incorporated on the right click contextual menu.
In terms of reproducing it just try using a laptop with a particuarly sensative touchpad...and I can gaurantee that you'll manage to flip the panel one side or the other.