Definitely strange. Go back into your KVM and make sure you setup the other side of your monitor so you can move the mouse continuously to the right and have it loop around to the main again. Here's my setup as an example. My machines are laid out like [far left=play2][left=work][main=play][right=johnpt2].

http://farm4.static.flickr.com/3210/...364089.jpg?v=0

With this setup, I can just mouse all the way around to the right and end up back on the left of my main. That may resolve your problem, as I know I have a similar rare/intermittent problem if I'm in the middle of rebooting one of my machines. Also, on both machines, set your Client-->General-->Retry value to 5 and make sure your "Release modifier keys when leaving client" is checked. That may help it recover. Out of curiosity, are you using DHCP addresses for your machines or static IPs?