1. Check that capslock is turned off
2. Make sure that numpad is disabled (by pressing the numkey). Laptops sometimes have a funny way of enabling/disabling this key so experiment. If it is turned on, you will see the light on the laptop. You sometimes have to press the function key (fn) then another key like F9 to enable/disable this.
3. Try logging into a virtual terminal.
Press <ctrl> + <alt> + F1
as the username, press enter then input your password (note you will not see the password being entered, it will appear that nothing is happening but it is!)
Also, to get back to the Graphical Interface use
Press <ctrl> + <alt> + F6