I use a hybrid system connecting my keybaord/mouse to my 6 computers with hardware and then isboxer to connect the clients to each other per computer.

This will of course eliminate your problem.

Check my signature over this week I am working on selling a usb splitter (be about $60 per computer including both the mouse and keyboard) and should get results soon. Limitations are the computers cannot send info to the keybaord/mouse (i.e. G15 screens) and they cannot be shut off (i.e. you always send keypresses to all computers) (although there is free software that will shut off all keyboard commands to your computer).