Server: Debian testing, with the 1.4.14 deb downloaded and installed. Client: Windows 7, with 1.4.14 downloaded and installed. Both are Premium.
On Debian, start the server with
synergys -f -c synergy.conf, because running it from the KDE menu makes it give an error "Option not supported on Linux: --enable-drag-drop" (and incidentally I can't find any file that might be telling it to use that option).
On Windows, run the client. Both are using encryption, with a simple password to be sure it's correct. The client says "WARNING: failed to connect to server: Protocol error from server", and the server says "NOTE: new client disconnected".
I haven't changed any configuration except the password, and 1.4.12 worked on the same machines just minutes ago.