This is rather an answer :o)

I use synergy 1.4.15 32 bits on a windows7 32 synergy server and synergy 1.4.15 32 bits on a windows 7 64 client. performed the local policy change on the client and now, after boot, CTRL+ALT+(FN/pgdn)BREAK gives me the login prompt. However, once logged in, the CTRL+ALT+BREAK doesn't work anymore (see XHO0407 conversation). The only case I need to use CTRL+ALT+BREAK is when I want to lock the pc when I leave it unattended for a while. You can easily use the arrow functions near the start/Shutdown button to chose one of the wanted functions... Switch user - logoff - lock - etc ... This is a nice work-around :o)