Did you try verifying local files?
Perhaps there is a problem with the main LevelCache folder? Do you have the same problem if you start a new game?
You could try browsing to the '..\Documents\Larian Studios' folder and renaming the 'Divinity Original Sin' subfolder (containing 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.
After starting the game and creating a new profile, try copying an old save from the renamed folder into the new profile, and see if you have the same problem. I think you would have to restart the game or switch profiles and back to get the save to show up, if you copy it with the game running.
