@Caravel - have you double-checked the borders of your new provinces? ie do your declared neighbours tie up with your border attributes? Check this by reviewing the "terrain armies crossing this border will encounter" right-click thingy - if this is the problem then it will CTD as soon as you hover over a border that is not declared for terrain but exists as a "neighbour" declaration. A bit unwieldy that sentence, but hope you get my drift

Other things to test: does .matteosartori. crash it? Does it crash regardless of what faction you play?