What you have sounds like the 'global variable bug' which causes the game to garble computer ressources (especially on computers with low memory), so that quests get respawned and all sorts of other nasty things happen.
What to do:
A) Get the patch (intl or US) to version 1.3.5512 at
www.interplay.com/bgtales
B) If you have 64 MB RAM or less, go buy some more.