So I recently installed the Windows 8 consumer preview to test some things out. NWN will not work without some tweaking so here's the troubleshooting steps I went through.
I have it running in compatibility mode with XP SP3
In the nwnplayer.ini I have the CPU affinity set to 0 (for multi core computers)
The preview will also install proprietary drivers and this will cause NWN to run like crap. AMD has released to a driver set for the preview and I have linked it below:
http://www2.ati.com/drivers/hotfix/win8/amd_catalyst_win8_consumer_preview_[rc10].exe
So if you are going to install the preview this is what I did to make sure NWN ran like it did before. Let me know if you have any questions.