Happened on my Windows 7 64-bit Synergy Server today...
Possible trigger... the whole machine hiccuped briefly as I tried to access an external drive that had gone to sleep. When the machine resumed, Synergy did not.
Solution:
- In Windows Task Manager I brought up "Processes, All users" and killed anything with "Synergy" in the name.
- I then went to "Services" and did a "Start" on the Synergy service.
- Then I restarted Synergy (the app) and it worked.
The order is important, because I tried to do those steps in different orders and it didn't work because the Synergy process keeps the Synergy Service from shutting down, etc.