I had a weird problem both in HD and regular, a frozen game during AI turn. Usually I know what it triggers it, resource overflow, digging for grail, summon boat without water skill, multiple teleporters but here I ran several erm tests and could not find any reason. Win XP, Era 2.4, HD 3.1.

1) Resources ok
2) AI can't move, so can't cast or dig
3) Stats and spells ok, removed all spell points from AI, same
4) Removed all market places from town, same
5) Reloading 1-2 months ago did not change the fact that on 4.2.5 game will froze.
6) Reloading from 3 months ago did not froze when 4.2.5
7) Game seems to froze on green turn, when I killed all green heroes, it froze on blue, and so on.

The only thing which allowed next turn was when I killed all AI heroes with erm. If you want to investigate this strange issue, here is the save
SAVE

The following mod is required to run this game:

TEW 3