OK, got it working. I'm indebted to you on two problems now, Ramones! I have to say that the community on these forums is super helpful and fast to react! They should have a badge for "props for helping" that users could give to their benefactors. <img src="smileys/smiley1.gif" border="0" align="middle" />
I got it working this time because I had an instance variable called "playerChatter" and just used Levels.playerChatter instead of Levels.Get("playerChatter").
The thing I was missing was that I mistook instance variables for keys in the case of a dictionary for some reason. Dictionaries seemed like a good solution to store static data like an in-engine version of a JSON file. Now that I'm looking at it, it seems that you can only set keys using in-game actions, so I can't set them up offline. And they must be in memory the whole time? Is that right? If that's the case, maybe I'd be better off using JSON or XML and loading them as I need them. Instance variables are easier, but it's a lame way to store dialog, and a waste of memory.