I have seen this problem on both my Vista server and Win7 server. Upon configuring the screens, then clicking start to start Synergy (in 1.4.3) the prompt flashes to "Synergy is running" but then straight away stops again, returning to "Synergy is not running". On both servers, the client functionality continues to work, but the only reason I'm using the Vista server is because the Win7 server did this as well.
The vista server was running fine acting as a server with an Ubuntu 10.10 client connected. When I noticed that Num Lock was being turned off every time I changed to the Ubuntu machine, I quit Synergy on the Vista server and changed the config for the ubuntu screen to turn on the Fix Num Lock option. I then closed the configuration, went to start the server again and now it has this same on/instant off bug. I have tried resetting all configurations to no avail.
Any way of fixing this?