Game crashes at launch. Win 8.1, all drivers supposedly up to date.

Allowed it out through the AV, but when it goes fullscreen completely crashes the PC (keyboard non-responsive).
Tried to run it in windowed mode (added -w option on the link target), but didn't help, still wants to go fullscreen.
Managed to catch it at one point in windowed, when it showed the main splash screen - press a button -, after that, it went again fullscreen and dead.
Tried to hunt for the settings.sav in the C:\Users\USERNAME\AppData\Local\Synthetik path, to try to edit the launch parameters in it, but the folder only contains six files named DownloadsNewsContent0-5 respectively.
Would appreciate some ideas on how to fix this.

Thanks in advance!