A KVM Switch and a missing mouse curser

I have a home network with 4 computers running on it. I have recently introduced a manaul Keyboard, Video, Mouse switch to reduce the clutter in my work room. The problem I have is that , when I switch from W2000 server or w2000 pro computers, then swithch back I lose the mouse curser. Keyboard and video control are all ok. The same problem doesn’t occur when switching from or to NT4 Server or Workstation or win9x. all the mice are serial mice. Two of the servers are based on AT motherboards sochanging to PS/2 mice is not an option. I have also tried swapping the leads over and using different ports on the switch.
Any Ideas?