Recently bought a rMBP and I'm unable to get my old IBM Model M keyboard working with it. I have a more recent Dell USB keyboard that works fine, but the IBM keyboard is not recognized. I should note that the IBM keyboard is PS2 (purple connector), and I'm using a PS2 to USB converter. This works fine on my Windows machine. When I connect it, I get the dialog that asks me to enter the key to the right of my left Shift key, says its looking for my keyboard, but never finds it. Any suggestions? Do I need a different PS2 to USB converter?