Keystrokes not passing through to server applications?

[Squelch]

I've been tracking an odd and inconsistent bug on a Windows based server. I have isolated two games that definitely suffer from this problem, and there may be other software that is affected. The problem manifests itself as a non or partially responsive keyboard, and seems to vary from title to title. Kerbal Space Program - Shift key does not work as a metakey (will allow capitalisation of text input only) Space Engineers - Total lack of keyboard response. In both cases, stopping the Synergy server will restore normal and expected operation, restarting will bring the lack of response back. Arma3 also seems to have some issues, but due to the miriad key combinations that are possible, it would be a lengthy process identifying which keys and combinations do not work. Each of theses titles uses a different game engine so this cannot be pinned to a specific technology (KSP = Unity3D 4.6, Space Eng = VRage 2.0, Arma3 RV 4.0) Turning on full logging (DEBUG2) I can see that synergy is capturing the keystrokes, and these are being passed to the clients normally, but it seems these are not being passed through to the focussed application on the server. This happens in both fullscreen and windowed modes, and setting "Don't take foreground window on Windows servers" on or off has no effect. Locking the cursor to the server's screen does not have any impact, nor does stopping the clients, so it seems to be entirely a server side problem. I have disabled or stopped all other 3rd party background processes that might affect the problem (screen overlays, screen recorders etc) and can certainly say that Synergy server is a common factor. This was never an issue prior to 1.7.x and possibly only a very recent introduction. Synergy 1.7.3, Windows 7 Extended desktop on two monitors. My question to the community is this; Are others experiencing this issue, and what titles are affected?