It happens to me sometimes.I usually use an application called Synapse for launching programs and finding files. Your friend can install it from the terminal with "sudo apt-get install synapse".
When his computer starts up without gnome-panel, he can launch Synapse with Ctrl+Space. Type in "terminal" to open the terminal.
When the terminal is open, enter "gnome-panel" and hit Enter. That should start the gnome-panel.
Others may have a simpler solution.
