Storms Of Zehir stutters badly whenever a character moves around the screen. More specifically, combat animation (characters standing in fixed position, using weapons) is fine. NPC movement by my opponents seems fine too (I think). It's only when PC characters move across the screen that rendering gets very choppy, like 2 or 3 fps choppy.

It happens in both combat mode and overland mode. I haven't tried the other modules yet for comparison. I have my other install (from cd) in a different directory, and it plays fine on my system.

I'm running in 1680x1050 windowed mode with a GeForce 8800 GTS 512. Water Reflections and Water Refraction are already turned off. I heard water was a problem in NWN1, so I checked that first.

Try using this:

http://nwvault.ign.com/View.php?view=Nwn2other.Detail&id=231

In addition to the Client Extension (which helped me), also check here. If you use an AMD processor, there's a special fix for low frame rates.
http://www.tweakguides.com/NWN2_1.html

water is not a issue in nwn2 however , shadows was, i turned them off the game was running way smoother after that

Turning off shadows is not a very optimal solution, though. There are ways of getting it to run smoothly without taking that (drastic in my opinion) measure, because I consider the shadows to make it look so much better than with them disabled. Disable antialiasing, if you need to disable something. You'll be able to run it at a higher resolution that way anyway. Install the client extension and follow the tweak guide to get the most performance out of the game.

Still no solution. I tried the client extension. I tried turning off/low every graphic setting available. No change.

Animations (stationary sway or combat attack) are perfectly fluid as long as characters (PC or NPC) do not walk anywhere. It's only during walking that screen updates stutter.

For what it's worth I have the exact same problem. I tried to above settings as well.

Everything is perfectly fine except for walking.

I don't think it's lack of computing power as its only walking that it happens on.

I have an AMD Firepro 8900 card. Dell M6600 laptop. 16gb RAM, can't remember processesor, but should be adequate.

This works but to anyone who says it doesnt. You must extract to your NWN2 folder. Then launch the game through the file named

NWLAUNCHER

not NWN2Launcher.

It doesnt replace files, it adds them. I had the movement stutter as well, but this fixed it.

You didn't say whether you tried the solutions given in the tweak guide linked above, especially those specifically for AMD CPUs.

While the Client did not work for me, yes I did extract it to the NWN2 directory. Restarting the computer did fix the problem. That was several hours ago and it has not reappeared. Perhaps the computer should just be rebooted after install. That used to be a normal practice, just gotten away from it over the years.

I can't speak to the AMD tweaks, I have an Intel CPU, so I didn't look into that much.

As siad though...It seems to be fixed with a simple restart.

Well, the info I found made it seem less about needing a restart after install and more about needed to do it any time the computer has been turned on for a long period of time. It may be something to do with the way the system clock or timer that the engine uses counts (wraps around or counting down when reaching the max value of the counter). In any instance, a restart every so often should be too bad.

Good news, there are 2 solutions!

Workaround:
Install the client update linked above by Sear, then run the NWLAUNCHER (not NWN2Launcher) in your game directory as suggested by ElCappaTen. It did actually work for me when I finally ran the correct executable.

Fix:
After installing the GOG game, reboot your computer. I'm in the habit of letting my Windows 7 system sleep, so I rarely reboot. After rebooting today, the regular application is working great. No need for the other client launcher. I upped all of my graphics settings to maximum again, and it flows beautifully.

Thanks for your help, everyone.

I wanted to add something as well; if you DO reboot your pc, don't use the client extension thingy afterwards, otherwise it can cause FPS issues. I was getting ridiculously low FPS rates and fiddling with all of the graphics options did nothing until I used the regular launcher.

I have the same problem and the client ext. didn't change anything. Updated my drivers and some graphical glitches vanished but not all. This is irritating, I played NWN2 often on this computer before wo problems but bought it here since my CD's got lost. Only thing that works is rebooting but it's hugely irritating to have to that again and again.
Can nothing be done?