Mouse issue with Win 7 / Linux set up

I have two pc's each with 2 monitors set up in a 2 x 2 grid. I will try and explain as bets I can

Left 2 are on a Win 7 64 bit PC running Synergy Server 1.4.14 Right 2 are on a Linux Mint 13 PC running Synergy Client 1.4.15

I can move the mouse from bottom left, up thru top left ( both Win 7 ), right onto top right and down onto bottom right ( both Linux ). I can move the mouse back thru the same route. Finally I can go full circle and move from bottom right (Linux ) to bottom left ( Win 7 ). However, I cannot move the mouse from bottom left (Win 7) to bottom right (Linux) Only the transit from bottom left to right fails. As I say, bottom right to left works fine.

I have tried placing the screens in different position in the server config screen, but no success.

Any help appreciated.

Andrew