Nvidia 980, latest drivers.
Win7x64.

Installed game on release. Updated to patch 635. Game starts unreliably. I'll skip the details.
Downloaded patch 639. Patch reports "does not support your version of the game". Please download installer."

Why no patch 635->639?

Gog's rules. For 2 days a patch to 6.35 --> 6.37 was available. After 6.39 release, Gog consider that every players have the 6.37 instal, so they just have to unleash the patch to 6.37 --> 6.39. 2 solution: galaxy updating...easy or download again the whole game.

Sorry