A previous hint suggested a hack for disabling the Keyboard Setup Assistant which has an annoying habit of popping up when using a KVM switch (whether a hardware switch such as the excellent Belkin Flip, or a software one such as teleport with a headless Mac). However, there is a less drastic solution that takes just one click and works with both 10.4 and 10.5 (it may also work on 10.6, but I can't test that myself).
Just click the red close button on the Keyboard Setup Assistant window, as per this Apple Support Document, and it shouldn't pop up again for that (virtual) keyboard. If you do need the Setup Assistant again, you can summon it using the Keyboard System Preferences pane.
Note that you may need to plug a mouse directly into the machine in question if your KVM switch is directing mouse input to another machine.
Mac OS X Hints