KVM messing my mouse

[david]

I've got a Belkin KVM that I use to switch between 4 boxes - one 
running Debian Woody/Windowmaker, one Debian Sarge without X, one 
MacOSX and one Ubuntu which I just recently installed.

When I switch from Ubuntu and back again, the mouse goes out of control 
- it moves and clicks randomly. I have to reboot the system to get it 
back. I think restarting X would do the job, but I don't know how to do 
that.

Can anyone suggest why this happens and what I should do about it? None 
of the other boxes have the same problem.

regards, David