Do you have a 32 bit version of Windows? If so, try shutting down all non-essential programs (especially anti-virus) before starting the game, to free up as much memory as possible.
Try browsing to the '..\Documents\Larian Studios' folder and renaming the 'Divinity Original Sin' subfolder.
This folder contains the saved games, configuration files and a level cache folder. Deleting or renaming it will get the game to recreate it on startup; playing the game from a different Windows user account would effectively do the same thing.
Please email supportdos@larian.com, with a description of the problem and the report.zip file generated by the
D:OS support tool.