When you say other keyboards don't work, you mean externally connected keyboards, right?
Make sure it's not a specific program that's stopping them, try with a few programs. If this doesnt work, reboot the computer and try in safe mode. Also, get a compressed air canister and clean your keyboard.
If the problem persists, try doing a system restore to a date before the problem occurred. This WILL remove any installed programs but keep your documents and files.
Start > Programs > Accessories > System Restore.