USB Apple keyboard doesn't work with ps2 converter?

I just bought a new apple usb keyboard today b/c i was sick of my old IBM from the 80s. I have a 4 port KVM switch that only accepts PS2. its been no problem before using usb converters, in fact my mx1000 converts from usb to ps2 perfectly. But for some reason when i hook up the new apple keyboard to the kvm via a usb to ps2 adapter, the keyboard doesn't work, it won't even work if i use the adapter right to a computer.

What the heck is the difference from an apple usb keyboard and a regular usb keyboard?

Thanks. Rob.

Maybe because the apple usb keyboard has a usb hub built into it that won't work through ps/2?