Plover and Synergy do not play well together.

From http://synergy-foss.org/ :

"Synergy is FOSS that lets you easily share a single mouse and keyboard between multiple computers with different operating systems, without special hardware. All you need is a LAN connection. It's intended for users with multiple computers, where each system uses its own display."

A user of Synergy writes:

"After I quit Plover, my keyboard acts as though it has its Control key held down. It also sometimes reverses the meaning of Caps Lock (when the keyboard LED is lit, it types lowercase; when the LED is off, it types uppercase). I thought that it had fixed itself after I toggled the Control and Caps Lock sufficient times. It let me type normally for a while. But when I went back to the computer after my coffee break, I couldn't get the keyboard to type at all. I pressed "T" and suddenly had many many tabs opening themselves, as though I were holding down Ctrl-T. I hit the Control key a couple times, which at least got it to type a capital T into the window instead. Then I unplugged the keyboard. T's kept appearing in the window, but that's probably ecause they were still in the buffer. I finally fixed things by rebooting the machine itself."