Balmorne's Pass won't end

Hi,

I recently bought Dungeon Keeper 2, and I've been having a lot of fun playing the main champaign. My progress has become stuck however because a bug makes it impossibe to complete Balmorne's Pass.

I've played it through several times now, and twice I have succeeded in excavating the entire map, killing all enemy units, and destroying all enemy traps. However even after doing that the game does not end. It just keeps going perpetually. Also, it says that occasionally enemies are getting through and escaping even though there are no enemies left on the map.

I'd really like to get passed this and carry on with the campegin, so please help.