Why can't I move my mouse to my other computer?

Logged on clients and server PC's show they are connected. Why don't screens switch? The title bar on the server screen turns grey when mousing to either side, but no client screen.

Update 1

I think I've done the config correctly. My server log reads:

2011-04-22T11:40:40 NOTE: started server ..libsynergyCServerApp.cpp,605
2011-04-22T11:40:40 NOTE: accepted client connection ..libserverCClientListener.cpp,130
2011-04-22T11:40:40 NOTE: client "System1" has connected ..libserverCServer.cpp,299
2011-04-22T11:40:41 NOTE: accepted client connection ..libserverCClientListener.cpp,130
2011-04-22T11:40:41 NOTE: client "Sys5" has connected ..libserverCServer.cpp,299

Screens don't change.

Update 2

For the record, the other two logs read:

2011-04-22T11:41:04 NOTE: connecting to 'System2': 10.0.0.12:24800 ..libclientCClient.cpp,115
2011-04-22T11:41:05 NOTE: connected to server ..libsynergyCClientApp.cpp,339

and

2011-04-22T11:40:50 NOTE: connecting to 'System2': 10.0.0.12:24800 ..libclientCClient.cpp,115
2011-04-22T11:40:50 NOTE: connected to server ..libsynergyCClientApp.cpp,339

I added the server address 10.0.0.12 after reading the Vukovic guide, but left the "if you have a domain running, you put FQDN" blank. My PC's are on a home network.

Thanks for your help.

Update 3

I also set up my ZoneAlarm firewall to permit port 24800, and in addition disabled ZA on both server and client PC's. All to no avail.