For the past few days, the on-screen keyboard runs, but only displays the first line (i.e. Tab, Enter, Space ... General). The rest of the alphanumeric keys are missing. The problem has not resolved itself through restarting the application or the PC itself. My tablet PC runs Windows 8. It's important that I have the keyboard so I can log on, because it is a touch-screen device. Please help? ):

Thank you for posting the issue on the Microsoft Community.

I understand that you have trouble using On screen touch keyboard on log on screen. I would definitely help you in fixing this issue.

Let us start with couple of questions:
1. Have you made any changes on your computer prior to the issue?
2. Does this tablet PC came preinstalled with Windows 8 or different Operating System?
3. Have you logged in to your Tablet?

If you are not able to boot, then I would suggest you to use Native touch screen and then try to login.
Follow these steps:
a. Press the “Ease of Access Button” in the lower left corner on your screen.
b. Choose the settings for your PC that you want to have available each time it starts.
c. Select On screen keyboard and set it as default.