I have 1 synergy client which has a dual monitor setup. The client is Xubuntu 12.04.3 and is using a dual screen configuration where each screen has it's own desktop, this is because the 2nd screen is a TV and I use it to watch XBMC (media center software) while I use the main screen screen to work in. I recently just started using synergy so I was able to get 3 computers all using the same mouse and keyboard BUT when I go onto the Xubuntu client which has the dual screens, I am unable to move the mouse to the 2nd screen, I need to move it over there to launch xbmc (by clicking the xbmc icon on it's desktop). Is it not possible to access additional monitors if a client has more than 1 screen? I can post my xorg.conf file if needed. It's an old Nvidia card, a MX-440. Has VGA out and S-Video output.
Since I am unable to move my mouse from screen 1 to screen 2 on the synergy linux client (the server is running Xubuntu 12.04.3 as well) I figured out a way to launch xbmc so that it opens on screen 2 if anyone else is interested. The command is [code]DISPLAY=":0.1" xbmc[/code] ":0.1" represents display number 1 (displays start at zero) and xbmc is the command to run XBMC. Good luck.