I am using Synergy 1.48 with a Windows 7 server and an OSX Lion Client. After bringing my mac mini back to work the mouse pointer would not show up on OSX. It still shows the mouse leaving and entering the Windows screen. I noticed tabbing between work spaces or windows with hotkeys would bring the mouse pointer back. It was working perfectly before this.
Here is what I did to fix this: -remove all extra workspaces from OSX -moved the dock away from the side of the OSX screen that was next to the Windows screen -restarted synergy client and server
I found this out because those were the only things I changed while I had my mac mini at a different setup. I tested it a few times and was able to reproduce this.