You didn't switch Windows users, or anything, did you?
Are you shutting down all non-essential programs (especially anti-virus) before starting the game?
Try starting the game directly from the '..\SteamApps\common\Divinity - Original Sin\Shipping\EoCApp.exe' program file. Perhaps right click and run as administrator (though there shouldn't really be restrictions writing to My Documents, AFAIK).
Try browsing to the '..\Documents\Larian Studios' folder and renaming the 'Divinity Original Sin' subfolder. This will get the game to recreate it on startup, and you can create a new profile.
After that, try starting a new game (just as a test), save, exit, reload and see if you have an issue with the the profile again.
If that works, you can just copy the saved game folders from the previous profile folder you had, to the new profile folder. Each save is a folder in the '..\Documents\Larian Studios\Divinity Original Sin\PlayerProfiles\<ProfileName>\Savegames' folder.