Long shot, but did you backup and restore those two saves to CD-R, so the files are marked as read-only? If so, select all files in each save game folder, right click, select Properties, and clear the read-only flag.
Check the number of files in the saved game folders, and compare it to the number in a working save at a corresponding point in the game (files are added to the save when first going to new areas, like Verdistis and the Dark Forset).
Try deleting all of the files in the '
..\Divine Divinity\Run\Dynamic' folder.
This folder is used as a cache for the game. Files are created / copied there from the save game folder when you load, and written / copied from that folder when you save a game. The files will be re-created as required the next time you start Divinity. If there was a corrupt file in that folder, deleting the files should fix the problem.
After this, try starting a new game (of the same character class and gender as the saves which will not load) and see if you can save and load. If so, try your latest save. If the new game works, but the latest save does not, there may be a problem in the saved game folder itself. If neither work, it may be a problem with Divinity, in which case re-installing might help.
See also;
Troubleshooting and Manual Install Procedure 
