The achievement decsription is to choose all replies in R'lyehian. As far as I have been able to tell, there are nine possible R'lyehian responses (I used JohnnyInterfnk's TA post as a basis for my list):

Chapter 9: Sarah Hawkins - When you first find Sarah.

Chapter 9: Officer Bradley - At the Hawkins estate in the upper part of the library.

Chapter 9: Sarah Hawkins - At the Hawkins estate by the fireplace.

Chapter 9: Algernon Drake - When talking to Algernon before or after retreving the amulet.

Chapter 11: Leviathan - In the jail, there are six R'lyehian choices to choose from...

Chapter 14: "Marie Colden" - 3 separate choices while talking to her.

Chapter 14: Sarah Hawkins -- Right at the end of the game, when talking to Sarah for the last time.

Here's the problem: I have played through three times, selected all of the above R'lyehian replies, and have not been able to unlock this achievement. I have learned that the achievement pops during the cutscene when you "Performt the Ritual." Am I missing a step? Are there any other conditions to this achievment? Is there anyway to add a numeric value to the achievement (i.e., choose all 9 replies in R'lyehian?) Any help or insight that could be provided would be greatly appreciated.