Yes. I just installed the game on a different drive – a clean version. It works fine from there.
Added 17 minutes later
Every cloud has a silver lining. After capturing the main castle, the campaign doesn't load any further. What should I do? All quests are completed, and I've cleared everything possible.
Or, it's better to wait for advice from those who have played through it; I don't know if this is the right thing to do (probably not).