Try browsing to your '..\Documents\Larian Studios' folder and renaming the 'Divinity Original Sin' folder (which contains the saved games, configuration files and a level cache folder). When the game is next started it will recreate the folder. Alternately, you can try starting the game from a different Windows user account.
If that lets you start a new game and save, you can move your previous saves from the renamed 'Divinity Original Sin' folder to the Savegames folder in the new one.
RainMakerXIII
Recreating the D:OS folder may also fix whatever the problem was with the second save game folder path. If it happens again, the game would appear to have issues with My Documents not being on an internal drive.
