Necromancer – “Ruler of Erathia” [Campaign 3, Mission 5]

Here's the issue I'm having. I've reached this mission, and problems started occurring. Narhiz arrives under the orange flag, I defeat him, and when I start moving the corpses, the game freezes completely. I tried not picking up anyone, but on the next turn, it still freezes completely. I was able to complete it before. Because of this, I can't finish the campaign. I have a licensed copy of the game. Has anyone else encountered a similar problem, or is it just me?