IIRC, in MM6 I needed help for the altars quest, and for solving the octagonal room in the Shadow Guild in the Frozen north. It also took me forever to find my way to Eel-Infested Waters. In MM8, I couldn't find the Book of the Sun for the priest's quest. And there were probably others, but it was a long time ago, and I can't remember.I had most trouble with MM7, though. I couldn't find my way round the Pit - I got thoroughly lost round there and in its dungeons. Especially, I had no idea what that blasted passage down there was doing to me, you know, the one whose destination varies depending on how many times you've been though it. The box got very close to a swift passage through the window at one point. 
