When I booted an eMachines 250-1162 netbook running Ubuntu 12.04 today, I was able to tab between fields on a webpage, but the touchpad was not working - I could not move the mouse pointer. I hit the Ctrl-Alt-F2 keys simultaneously to obtain a console window where I entered the following command:
$ gksudo modprobe -r psmouse (gksudo:2607): Gtk-WARNING **: cannot open display:
I then switched back to the graphical user interface (GUI) console by hitting Ctrl-Alt-F7. I was then able to move the mouse pointer using the touchpad.