I am assuming that this is a laptop.
First of all have you checked that the keyboard has not been locked? I have taken this from the Toshiba satellite forum...
"To unlock the keyboard on your Toshiba screen so that you are able to type in on your log in screen, Press CTRL+ALT+Del twice on the keyboard. Type in your username and then hit the tab key, type in your password and then press enter. This should enable you to log in to your laptop as usual."
Did you try
restarting and tapping the F8 key to get into Safe Mode. Once in Safe Mode, choose the "Boot With Last Known Good Configuration" option ?
Sometimes if you power down, take the battery out for a few seconds, keep the power on button pressed for a few seconds, replace the battery and power up the situation corrects itself.