However, what you are trying to do may be possible. I did have a degree of success with dynamically loading scripts which handled Said()s and disposing of them as soon as they were unneeded (IIRC lots of Unload or DisposeLoad calls).
I have a feeling this is the solution I need. So far I've moved all of my dialogue scenes into separate (but identical) rooms you go into when you begin a conversation, where there's only dialogue interaction. This seems like a smarter way of implementing the same idea!
I was thinking of separating the dialogue into separate scripts (say have a "who is" script with all the possible characters, a "what is" script for every possible noun etc) it'd be a lot of work, but I think worth it. I like the 'dungeons and dragons' feel of the parser when it feels like the options are limited only by your imagination, so i think that's the way to go, time to learn a bit more about memory management...
I'll take a look at Tex Murphy and see what you mean about that...