Here are possible fixes and workarounds that might help. We are still investigating these, so check back after a while if your issue isn't resolved.
CHANGE DISPLAY MODE (FULLSCREEN vs BORDERLESS WINDOW vs WINDOWED)
Please try the different modes to see which works for you. Borderless window is the default option, and is the most compatible one
While it's a natural instinct for PC gamers to switch to fullscreen, please resist this temptation if you see the game crashing on you, after setting this option. ;)
UNPLUG SECONDARY MONITOR (IF USING MULTIPLE DIFFERENT MONITORS)
We suspect that The Witcher 3 cannot handle a situation where you have two monitors, and they have very different refresh rates. Even if this isn't the case for you, try physically unplugging your secondary monitor, and launch the game.
CHECK FOR INTERFERENCE FROM GOG GALAXY (NOT CONFIRMED)
It's possible that this happens due to anti-virus/firewall software blocking Galaxy. Make sure to add Galaxy to your security software's trusted applications list.
If it doesn't help, please try the following: 1) Shut down GOG Galaxy,
2) Go to the game's binx64 subfolder (by default: C:GOG GamesThe Witcher 3 Wild Huntbinx64),
3) Rename the galaxy.dll file, or move it to a different location.
If this helps, contact us immediately to confirm this.
UPDATE YOUR DRIVERS
Always make sure to have the most recent WHQL-certified (and non-beta) drivers for your card. You can find them here, depending on your card manufactuter:
NVIDIA (the drivers from 2015.5.18 are the first ones speficially tuned for The Witcher 3),
ATI (AMD). We generally do not advise auto-detecting drivers. Ideally, please select your graphics card manually to find the right driver for you.
DISABLE GEFORCE EXPERIENCE
If you use GeForce Experience, please make sure that you disable Shadowplay before launching the game. If disabling Shadowplay wasn't helpful, please disable GeForce Experience altogether, and make sure that you reset graphics device settings after that. To do this:
1) right-click on your desktop and select Nvidia Control Panel,
2) click Manage 3D Settings,
3) in the upper-right corner, click Restore Defaults.
To disable GeForce Experience, find its icon in your system tray (lower-right corner), right-click it and select "Exit".
CHECK MINIMAL REQUIREMENTS
Make sure that you meet the minimal requirements. The game will most likely crash without an error message if your computer is below the requirements. You can find them here, on the official CDP RED website. Please note that desktop graphics of any kind are currently unsupported.