Thread necromancey for the win. Seriously though, I do know one reason why this happens and it most likely isn't the only reason it happens but as a programmer I can validate why and how this happens when using keyclone/octopus on two computers with kvm enabled.

In this example I'm running my main main paladin on one computer and my 4 shamans on a second computer. The keyboard and mouse are cross linked to the two computers and wasd only go to the client that has focus. If I hold down for example the w key and move my mouse over to the second computer the w key basically gets locked in a pressed down state on the paladin client and will not release without first going back to the paladin client and hitting the w key again.

Now as to why this happens it is very simple. What is happening is Octopus is sending the WM_Keydown windows message directly to the paladin client. Keys stay pressed until the corresponding WM_KeyUp message has been sent to the window. Because the W key is pressed down while the paladin screen has focus and not released until another client has focus the WM_Keyup message is never receieved and the Paladin continues happily running off into the sunset. Going back to the client and pressing the back button does no good because to this client the W key is still being held down. Pressing the W Key again works simply because it causes the WM_KeyUp message to be sent after you release the W key with the proper client having focus. I hope I explained this so people can understand it.