I believe this is a well known issue, but correct me if I'm wrong.
* [Bug #2408 - SHIFT key stops working on Mac OS X client][2]
* [Task #19 - Sticky modifier/meta keys (shift, ctrl, alt)][3]
* [Bug #2743 - Modifier Keys don't work on Mac OS 10.6.4 client][4]
* [Bug #2842 - Right shift broken (Windows server, Mac OS X client)][5]
* [Some keys not working after Mac OS 10.6.3 update][6]
* [Synergy 'Shift' key not working on the Mac][1]
[1]: http://superuser.com/questions/239027/synergy-shift-key-not-working-on-the-mac
[2]: http://synergy-foss.org/pm/issues/2408*
http://synergy-foss.org/pm/issues/2408
[3]: http://synergy-foss.org/pm/issues/19*
http://synergy-foss.org/pm/issues/19
[4]: http://synergy-foss.org/pm/issues/2743*
http://synergy-foss.org/pm/issues/2743
[5]: http://synergy-foss.org/pm/issues/2842
[6]: http://groups.google.com/group/synergy-plus/browse_thread/thread/66309a0842fc1e62