I've tried to use those adapters with KVMs before. The LinkSys brand KVM I had was only guaranteed to work with Windows! I tried Linux on the same PC and it would not get the mouse stuff working through the KVM.
However, try looking for a KVM that is tested to work with Linux, and I'll bet that it works for you. I've got a different KVM now that works with both Linux and Windows without any real problems. But since my A3000/CSPPC died a year ago I can no longer try it with my PS/2 mouse adapter. :-(