I went through my setup again, and this time found a disco, which, when fixed, allowed VNAV to work again.

It seems hit and miss though, but I'm getting there.

I've completed three very nearly perfect flights in the CS777 today, and I think it comes down to very careful CDU setup and route planning. Make sure the waypoints and their speeds / altitudes are correct, and then be vigilant with the VNAV button, as this tends to disconnect during the climb as and when waypoints are reached.

I'm not saying that it's more difficult to setup than any other aircraft, but I double check my flight plans and entries, and I don't rely on on SID's / STAR's in case there's a clash, alt discrepancy etc.

I'm just beginning to really enjoy this aircraft.