I'm also having this problem and indeed it was related to Skalds, good thing I found this thread. :)

it's the "last hero" spell that bugs everything... if a unit with this buff is hit, you crash ^^
you'll have the same with heat focus later =)

Though the bug is solved now - No, it wasn't the Skalds that caused it. You do not get any Skalds on Nordling anyway, so I dunno why anyone assumed this.

Because he often has Skalds in his army when you fight him...

Oh, I see. No, in the 2 cases I got to him he didn't, and even when he did, the game froze whenever one of his other unit acted.

Is Last Hero still bugged? I noticed Skalds do not cast it, and I found the spell but could not purchase/try it yet. (Though the whole delayed 125% damage thing is not really a sweet deal, anyway - you'd need to dispel the spell if you want to use it to full effect).