Thanks for the quick answer Raze. It's a Steam version and the integrity of the files is fine. I've started the fight a third time and this time I was lucky (I did not have any summons this time, not sure if this might be a reason).
The crash did not happen the instant the dragon was killed, but I believe it occurs before the animation is supposed to start. In any case, I've sent my save and my dxdiag file to the email address that you've mentioned. If there is anything else that you might need for your investigations please let me know and I'll try to help.