I used to have this problem, and it may be a Multi-Core issue.
Fixing it, for me, involved going to my NWN root folder and finding a file called nwnplayer. I backed up the original into a seperate copy, then opened it in notepad.
Under your game options there should be an Option that reads
Client CPU Affinity=1.
experiment with changing this to 0, -1, or -2 to force your CPU to run a single core (don't worry, NWN is so old it can handle it)
This completely fixed all crashing issues for me.
NWN seems to behave very unpredictably on multi-core computers. I've heard half a dozen different ways that multi-core would ruin NWN.
I think my favorite was how it sped up singleplayer by a hundred times, so a monk with flurry of blows got something like 30 attacks per second.