If my computer goes into sleep mode, the keyboard may or may not work for the login screen. But once logged in (if it works), then it will not work after logging in. I have to restart at this point. Keyboard filtering is not the culprit on my computer (another question asker solved his identical issue by disabling keyboard filtering), and I am at a loss as to a solution. I am an advanced Windows user, and I just can't figure it out... I'm still frustrated at the fact that I have to re-install ALL of my programs after my Win 8 upgrade, despite the compatibility program saying most of my stuff was just fine before the upgrade.
I have this problem on my Windows 7 laptop. I have to login using the accessibility on screen keyboard, and then put my computer back into sleep, wait 1 minute, and wake it up again (by pressing the power button). The keyboard is then working after this.