Ok, when you say it doesn't work, do you mean the extended hot keys, or the whole keyboard? Extended keys are notoriously hard to deal with on KVMs because the kvm has to fool the computer into thinking the keyboard and mouse is always connected, so it uses a "standard" keyboard emulator to do so. I've had experience with extended keyboards that work fine if you boot with the KVM switched to that box, and don't switch to another, but most of them lose the extended functionality once you switch to a different machine and switch back again.
One solution is to keep the good keyboard directly wired to your main computer via usb, and get another one for the KVM, that way you don't lose functionality on your main computer. Another solution is to get a KVM that fully supports USB keyboards, and they tend to be more expensive.
HTH.