Are you maxing out the level of the characters too? If I remember correctly the some of the sidequest conversation scripts record the xp level that you (or the NPC) is at and the next sequence checks to see whether you've an increased your level before it initiates. If you're already at level 20, then you wouldn't be able to sequence through the dialogs.
If my memory is wrong here, I apologize. I'm on my laptop without KotOR installed.