CrazyEyes: Sorry if I'm bumping an old thread here, but I had a similar issue and managed to solve it. I had a savegame from a prior BGT game, but when I moved it to my current installation the NPCs in my party all used the wrong voices and made the wrong comments (action comment for selecting them, etc.). This is pretty much the only place on the internet i could find someone with my problem, so for the sake of future Google searches I'll put my solution here. :)

I noticed that if I started a new game, the characters sounded fine when I met them. All I ended up having to do was spawn a new copy of each NPC in my party using the CLUAConsole:CreateCreature("<name>") cheat. <name> is just the first six characters of the NPC's name. The party members I spawned had the correct voices and dialog. When I talked to them, they spoke to me as if they'd never met me before (Minsc wanted me to rescue Dynaheir, Coran wanted me to kill wyverns, Branwen was still petrified, etc). I don't know if this will cause problems with their personal quests later on, but everyone joined my party.

When I spawned them, they also spawned at what seem to be their lowest experience levels. I ended up having to reload, write down all their experience (and in the case of my mages, learned spells), then spawn them again and level them up. Slightly tedious, but well worth it as they all seem to work fine now.

Hope this helps.