Keyboard Some Keys Not Working?

I am having a problem with some keys with my HP computer. Some keys of my keyboard stoped working all of a sudden.

It's the line of "h,j,k,l" keys that are not working. All of these keys are in the middle of my keyboard. I have opened the keyboard and the contacts are fine. Any ideas what's going on?
How can I make the keys of my keyboard to start working again?

Verify that the key is not working in more than one application. It is possible that some keys of the keyboard may not be used in all programs. This generally always applies to the Function keys F1 through F12.

If not all keys are working in all programs and you have Windows, attempt to boot the computer to a MS-DOS prompt or Safe Mode and test the keyboard in DOS.

If it broke and it won't be working any way, you can launch the on-screen Keyboard or “Virtual Keyboard”
do the following:

* clicking start->run… and type osk then hit enter. OR
* clicking start-> programs – > accessories – > accessibility – > On-Screen Keyboard
* Alternatively, you can open c:WINDOWSsystem32 folder in Windows explorer and double click osk.exe

This way you'll have a virtual keyboard in your screen