EDIT: Sorry for the OT replay. While related to gfx, it's not nv-only.
Wild guess :
[snipped what MA may and may not have modified]
What many fail to consider (seemingly MA itself when they started) is the (almost unbound) large amount of different textures (and shaders?) in areas where many avatars with different clothing/armor/tools/<whatever> are.
I may be wrong, but I think EU is the only MMO, or at least application of the CE2 engine, not having everything compiled down to "levels"/"maps"/<whatever>, making it relatively straightforward for "the others" to throw away even leaked buffers on "area change". EU is a slightly less static environment.
While I haven't experienced the specific issues after switching to the 64-bit client, while on 32-bit it often seemed like the client loads up all mipmap levels of all textures for an avatar just entering visual range; even if you can't even see the avatar, it could load up megabytes+ of textures, and hog VRAM until it crashed due to VRAM exhaustion. Even if that speculation is wrong, the client at least
wastes tons of memory, that much is clear.
You made me laugh with the idea about where the "AI" came from. I didn't know Irrlicht was in such a sad state in that area. ;P