It's the OpenGL support (or non-support may be more accurate) of the newer drivers. Not just OpenGL as an API but a version that is compatible with your card's driver choice. Different versions of the Catalyst can be adjusted to adapt to the demands of NWN's rendering method, though I've never had any luck myself. Not necessarily a matter of capacity or speed but the way the system responds or "digests" function calls from the game engine. It's likely that the added graphic demands of the newer versions of NWN pushed the ability of your existing driver beyonds its limits. It could have easily worked just the reverse for someone else... not working properly until v1.69 had been applied.
So it's not the old card working fine and the new one having issues so much as the driver support for the same rendering method that is the key. Have you attempted to revert to the driver version that worked well with your older card?
Even if that resolves the NWN problem, it may render other apps poorly, which ends up becoming the Catch-22 reality. It just depends how long the card/driver engineers feel they should support older rendering methods while still providing leading edge performance for the newer products.
Different card manufacturers have provided different degrees of this legacy adaptability. There are loads of threads in the tech forum dedicated to investigating how the performance can be optimized for different manufacturers and card versions thereof.
Even something as basic as to how security and virus protection programs treat the game file writing can affect performance. .
That's about all the advice I can suggest. As the technology continues to depart from what was practical in the previous generations, it will become harder and harder to get NWN to work reliably, and it shares this characteristic with other ancient games (BG crashes all the time for me on this slightly newer machine while NWN is smooth as silk
'> ).
So the bottom line is: Whatever you find that works, post it. Publish as detailed an account of your system and hardware specs as possible and precisely what you did to rectify the issues so that others can identify your contribution as a viable option for their own situation. .If you have time, edit your topic title to reflect the general characteristics (like including
"XP", "AMD HD6850" & "quad core" wouldn't hurt) so that it is easier to spot by
others in the community or first timers looking for answers. Trust me. It really helps.