Actually, I just had the exact same problem, but thanks to a tech-savvy friend I got it fixed.
The cause was, apparently, a corrupted save file. When my friend realised this, it was easy to fix: I just found the folder containing the save files (in my case, My Computer/C:/Users/Owner/Documents/Paradox Interactive/Crusader Kings II/save games) and removed most of the saves, except the latest ones. Fortunately, the corrupted file was not among the most recent ones, so once I did that, the game started working again, just nicely. No need to reinstall or anything, just delete most (not even necessarily all) of your save files. And I even got to continue my current game, with no apparent errors.
Well, it worked for me at least.
(Also, funnily, I discovered that I don't even have to exit the game while modifying the "save games"-folder, once I played with the files Crusader Kings immediately updated as to which files were actually in the "save games"-folder. Inconsequential, but fun)