For Christmas for I was given the MX Duo. I installed it just like it says in the instructions but nothing worked. Since then, I've figured out that the mouse will work as long as the keyboard is not plugged in. If the keyboard is plugged in, neither the keyboard nor mouse works. This is true for both PS/2 and for USB. Is there something I'm missing or is something defective? Batteries in both are new and there's not a distance problem with the receiver.