look in device manager for errors
look in Event logs for errors

did you spill something on it ?

what make laptop. .. assume xp ? some laptops have key combo when you press you switch to a real keyboard,, some work instantly with a usb keyboard. Try one.

no spills, acer aspire 3000, windows xp

Try pressing at the same time
Fn + F11
thats sort of the num lock sequence that changes the keyboards middle group of keys to a keypad,, does numbers rather than letters ... maybe you've done that by accident ?

We think it is a battery problem. My DH took the battery out and all is fine! Thanks for your help!

I have a dell inspiron 2650 that on ocassion wants to balk on me. Disconnecting wall plug and THEN removing battery for about one second has remedied a lot of problems. Grady

I have an ACER Aspire 3050 laptop and had the same problem with the touch pad and keyboard.
I know this may seem simplified...but before you run through all the issues/processes offered to help your keyboard/mouse react again, try charging the battery for a night or two.
The laptop did not work at full function right away (after the first night of charging) but did show some signs of improvement, like some aspects of the keyboard reacting.
I had not used my laptop in a while due to a programming issue. By the time I had it fixed, the battery went dead. If the keyboard works without the battery in, after you finish working on the laptop, try keeping the laptop powered on with the battery in it when you are away or asleep.
This will very likely charge the battery again and restore function to your keyboard.
I am using the laptop keyboard to write this with what I originally thought was a corrupt battery, now functioning just fine.
Remember, I noticed the night before that some keystrokes were showing, where there was no reaction before. The battery took more than one night to be up at full power...but it is fine now.
I saved myself more than $40.00 by not purchasing a replacement. Hope this helps. :)