A few that I found that required a bit of "suspend disbelief" to them are;

When you speak to Harani on Khenarthi's Roost anouncing the Silvenar's death you say "The Green Lady suspects murder". Then Pelidi - with Unlandil standing right next to him -does his tirade on betrayal. Ulandil HAD to have heard "The Green Lady suspects murder" yet confronted later says the "Green Lummox and his mate are dead" when he should know she was alive.

Another is the Plague of Phaer when Hendil is confronted in the cave and says to tie him up and "I won't run". So, you tie his hands instead of his feet (or both)

Also, when you free Lyris the Prophet says from the looks of her she appears unharmed - when he is supposed to be blind.

What are your favorites.