Did you try saving before triggering the auto-save, exiting the game, restarting, reloading and trying again? That could help if the issue is related to low memory on 32 bit systems.
Did you try deleting the first 2 auto-saves, and anything that the game may have started writing for the third? (in the game, or to be sure in Windows Explorer after browsing to the '..\Documents\Larian Studios\Divinity original Sin\PlayerProfiles\<Name>\Savegames' folder)
Did you try verifying local files for the game?
If you zip your save and email it to me (raze@larian.com) I can try it here (if you don't have access to another computer). That should get you past this particular auto-save, but wouldn't be a very convenient solution if subsequent auto-saves also hang.
