For those playing the current build that can still not correctly save and load games here's a temporary solution to help you out until Larian can get their hands in and sort it out finally.
Browse to: Documents\Larian Studios\Divinity Original Sin
Open the game, start a new game, then minimize once you're standing on the beach.
Back in the folder, if: Documents\Larian Studios\Divinity Original Sin\LevelCache
Is not present then create the LevelCache sub-folder, and inside of it create any random file, .txt, .jpg, right click on it and select properties.
In properties, under general, set the file to read only, hit apply, and close the window.
After all of that you should be able to save and load games without issue.