If that doesn't help, check the number of files in the save game folder (in '..\Divine Divinity\Run\savegames'). A new game should have 22 files, after going to either Verdistis or the Dark Forest it should have 27, after going to both it should have 32, after getting to the wastelands it should have 37, and after getting to the Black Ring dungeon it should have 42.
If you backed the save up firectly to a CD-R, make sure you select all of the files in the save folder, right click and select Properties, and then clear the read-only flag (checkmark in Win 9x, green box in XP). If you zip saved game folders before backing them up, they will not get marked as read only, so you only need to extract them back in place.