I got the same problem and I found a solution.

Just uninstall the keyboard driver and then restart the computer, following these steps:

Windows XP:
1. Right click on My Computer
2. Click on Properties
3. Click on tab Hardware
4. Open the Device Manager
5. Open the Keyboards list
6. Right click on the keyboard and then Uninstall it
7. Restart your computer

Windows Vista / 7:
1. Right click on My Computer
2. Click on Properties
3. Open the Device Manager (top left)
4. Open the Keyboards list
5. Right click on the keyboard and then Uninstall it
6. Restart your computer