Good point... which am I talking about. Looking at the specs, the card does support non-power 2. Is it common for non-square textures to be unsupported?
No, I think the last card that didn't support non-square textures was a Voodoo 3 or something. That's why I asked, because it's so unusual it would suggest a driver problem or something.
Lack of support for non-power of two is much, much more common, and I'm surprised that 6600 does actually support it. Assuming the specs you're reading are correct, I would suggest that it's unlikely either of these are your problem, but it could be a driver issue still. I assume you're already updated as much as you can be with Nvidia's drivers?
Are you 100% sure that the game uses NPOT textures or is that just forum talk?