Please email supportdos@larian.com, with a description of the problem and the report.zip file generated by the
D:OS support tool (for the PC version). The report will contain system and game information, any crash dumps, and your saved games (if you were previously able to get far enough to save). If file size is an issue, any saves can be deleted from the zip file, since they are not relevant in this case.
Did you try lowering the game resolution, or switching it to run windowed or fake fullscreen mode?
Did you try verifying local files (for the Steam version)?