Found this on a HP netbook, so I am hoping it is similar to your Asus:
As far as know with HP machines there should be a lock key near the LCD screen. To disable the keyboard lock, hit the key and simply enter the User Password to unlock it.
The only other way i know is to power the laptop off, remove the power cord and the battery, then put the battery back in and power the laptop up again, that usually brings the keyboard back to life. You can however use the on-screen keyboard if none of this works.
If this doesn't help, let me know and I'll dig some more. HOOAH!!!