I'm currently working off two Windows laptops, and a wireless mouse connected to one of them.
SInce I keep flipping between screens, I find myself using the keyboards of the laptops themselves, rather than using a single machine as a host and the other as a client.
This works fine for keyboard input, but it seems every time I type on an alternate machine, Synergy switches to consider this machine to be the master. If the mouse is plugged in to the other laptop, I find the pointer gets