Did you install the Logitech K120 SetPoint driver? That's probably where your keyboard issue is occurring.
Go here to download it:
http://www.logitech.com/en-us/434/66...s&bit=&osid=14
Try that and see what happens now. You'll need to choose between either the 32-bit or 64-bit SetPoint driver. Make sure the keyboard is plugged in to a USB slot during the install and then do a reboot and see how it works out.
Also make sure your keyboard is plugged in directly to a USB port on the motherboard's input/output panel on the back of the computer.