Make sure you exit all non-essential programs (especially ant-virus) before starting Divinity.

Try starting a new game and saving/re-loading it. If that works, there may be a problem with your saved games. Some things which can do this are; (links to old forum)

missing file - Found out what is the savegame bug !!!

read only - Load crashes

version number corruption - savegame version misery and the FIX!